JoeViking245

The default location change in version 13.21 with the advent of Media Packs.  You can find more information about them here:
LaunchBox Media Pack Feature – Version 13.21 - LaunchBox

(I'm guessing you're meaning /LaunchBox/Emulators/RetroArch/)  No. It's not. 
If for some reason it truly is missing on yours, then I'm surprised RA even opens. As in it's probably a corrupt install.  If that's the case, have LaunchBox reinstall it for you in Tools - Manage Emulators. 
Otherwise, right-click a game using RA and follow the red boxes...

Update your local database
Tools < Download < Force Update Games Database Metadata...

Anything's possible.
To test, you could try removing the contents of your emulators \UserData\ folder.  Then copy the contents of your \AppData\Roaming\BigPEmu\ folder into it.  Then use the %romfile% -localdata parameter(s).
If that works, you can remove the /AppData/Roaming/BigPEmu/ folder.

Clear Logo folder location changed as of version 13.21.  Can read more about it here:
LaunchBox Media Pack Feature – Version 13.21 - LaunchBox

If you had LaunchBox install MAME for you, there should be some scripts in the Reset, Save and Load sections.
 
...and if those scripts had been in there, you could look at the one for Save, where it takes a modifier key and another keypress to activate.  Modify that script to suit your needs and you'd get
Send {Alt down} Sleep 50 Send {r down} Sleep 50 Send {r up} Sleep 50 Send {Alt up} The key here (no pun intended) is setting a Key Delay which is needed for some emulators.  Essentially, you're causing a more pronounced key press(es).
I haven't tested this in Supermodel because like any Arcade game, I don't save.  We call it "old school".   But I suspect it will work.  

For games that don't use a [traditional] emulator such as Steam, you can override the startup time on a per game basis or Bulk Edit the games and set them all at once.
To bulk edit them, select all your Steam games (e.g. in the Windows platform, click one then press Ctrl+A) then press Ctrl+E to start the Bulk Edit Wizard. 
For the Field select Startup Screen - Enabled and check the box.  When prompted for more changes, select Yes, I would like to make more changes.  For the Field, select Startup Screen - Load Delay. Then adjust the value accordingly.

When you select multiple game then go to Tools < Download < Update Metadata and Media for Selected Games..., you want to leave checked Search for game information in the local metadata database (recommended).
On the next screen (and 2 if you have an EmuMovies account) select the image you want to download.  
Then select Yes, but do not replace any existing fields or media (recommended). And Finish.
 
This will only update the games you selected.

It's because you have emulation enabled.  So it's trying to pass the script to RSPC3.   Go to the Emulation section for the game and uncheck Use Emulator.

The Default Theme has "built-in" fallback images that it looks for.
Steam Screenshot Epic Games Screenshot GOG Screenshot Amazon Screenshot Origin Screenshot Backgrounds Screenshot - Gameplay You can change (add or remove or re-prioritize) the Background Image Priorities under Tool - Options. (This is where you might add Arcade-Marquees).
 
It's hard coded into the theme.  But has an easy work-around.
Make a copy of the \LaunchBox\LBThemes\Default\ folder In your "copied" folder, open the file \Views\GameDetailsView.xaml with any text editor Look for <!-- TOP BORDER OVERLAY --> Delete it and the next line Save and close Open LaunchBox Set the Theme to-use to the "copied" folder Theme Name (which may be "Default - Copy") Instead of editing that file, you might be able just delete the image file \LaunchBox\LBThemes\Default - Copy\Images\Overlay.png. 
I don't know if simply deleting image file will throw an error or not. But editing the xaml will for sure work.
Regardless, you will need to make a copy of the Themes folder in order to make any changes or file deletions. 

Do you have the corresponding .chd file for the game?  Is the folder holding the CHD file in the same location as the ROM?
/Games/Arcade/sf2049.zip
/Games/Arcade/sf2049/sf2049.chd

It can be.  But mostly (aside from programming knowledge) time.
You can always Request A Feature (above under Help & Support).  Be specific.
See here and remember to upvote it as deemed necessary.
Feedback - LaunchBox

The error message seems to be missing some data. aka can't see the whole message to be able to best decipher the actual cause.  For future, you can copy and paste the whole text that's in the message.
Lately, that type of error message depicts that's there's an issue with a 3rd party plugin. You can try removing them from the Plugins folder. (the 3rd party plugins, that is. Not LaunchBox's plugins)
Or, to change the Theme, you can edit /Data/BigBoxSettings.xml.  Look for <Theme> and change the value to Default.  e.g.  <Theme>Default</Theme>

Assuming with your premium license you've updated to at least v13.21, you can read about the new locations here:
LaunchBox Media Pack Feature – Version 13.21 - LaunchBox

System Menu < Options < General < Skip Game Details Screen
But this way you'll never see the Game Details screen unless you change it back.
Instead, you could also map a button or key to "Play" the selected game (skipping the Game Details).
System Menu < Options < Controller Mappings < Play

According to some recent posts on LaunchBox Discord and a 2 year old post on LaunchBox reddit, you need to add the games to 3dSen itself, 1st. 
It then saves game info into a rom.json file.  Located somewhere in [%appdata%\..\LocalLow\Geod Studio\3dSen]
After the games have been added, open the json file with any text editor.  An example node looks like:
"id": "64", "romPath": "C:\Nintendo NES (3dSen) Games\\Mega Man 3 (USA).nes", "title": "Mega Man 3", "lastTime": 1692883659 Look for the game and get the id number.  Edit that game [that you've already imported into LaunchBox] and in the Emulation section, it should already be set to use your 3dSen emulator [that you've already installed into LaunchBox].  Check the box for Use Custom Command-line and in the box below it, put in -id=64  where "64" the id number you found.  Save. Close. Play
Yes. You'll have to do it individually, for each game.
 
For me, this is all hearsay.  But @ci2own says it works.   

Without overthinking it...
$Esc:: { WinClose, ahk_exe {{{StartupEXE}}} Sleep, 5000 WinClose, ahk_exe {{{StartupEXE}}} }  

You're not blind.  Or... we both are.  
Depending on what you wired the Mute/Unmute button to and what mode it's in, you might be able to create an AutoHotkey script that you have run when you start LaunchBox and/or Big Box. For this (possible) option to work, you need to know what your button is mapped to.
Example: Your encoder in keyboard mode and you have the button mapped to "M" (again, just an example).  The script would look like
m::Send {Volume_Mute}  
 
To use the built Pause Screen, set the pause button.  Note: LB and BB require separate mappings.
LaunchBox:   
Keyboard Mode:  Tools < Options < Gameplay < Game Pause XInput Mode:   Tools < Options < GameControllers < Mappings - Show Pause Screen Big Box:   
Keyboard Mode:   System Menu < Options < Keyboard Mappings - Show Pause Screen XInput Mode:   System Menu < Options < Controller Mappings < Show Pause Screen  
Once that's all dialed in, take a look around at all the other cool things you can do from within the Options Menu(s).  

In your \LaunchBox\Images\Media Packs\Platform Clear Logos\Nostalgic Platform Clear Logos\Playlists\ folder, for your example image, what is the file name?
Nintendo 64 Fighting.png Fighting.png (Green is good. Red is bad.)
 

LaunchBox doesn't natively import MAME's softlists.  That said, (some/most/all) softlist BIOS and Device files are in with the MAME full Arcade set. (just not the softlist game ROMs)
If you use the MAME Arcade Full Set Import Wizard, on one of the screens is a list of items to check/un-check.  One of them is Skip Games Unplayable in MAME (or similar).  Unchecking that will import the miscellaneous file you're [most likely] seeing.
If you don't want to reimport, you can click the filter icon (when in your Arcade platform) and select Genre - System - BIOS and delete the resulting files.  Do the same with Genre -System - Device.
I say "delete" (in LaunchBox, that is) because they do you no good and you can't play them anyway.  If you want to "Hide" them instead, select All of the above resulting filtered files and press Ctrl+E to start the Bulk Edit Wizard.  Then select Hide and set it to true (or however it's deemed).

Just tested. No luck.  Force updated the local database, then all 4 were found.

Yes.  Easiest way is to right-click the Arcade platform and click Delete.  When it asks to delete Images (2nd popup), click no.  Move all (the rest of..) the files (and chd folders) into /Games/Arcade/.  Then run the Arcade Full Set Import Wizard (and it won't ask if you want to move the files. ).

For Steam, last I read you can add the parameter -silent.  Whether it's still valid in 2025, not sure.
For apps that just hang out in the background waiting to be used/triggered, you should be able to:
Create a shortcut to the app Right-click the shortcut and select Properties Next to Run: change it to Minimized Click OK to save Then point your Startup to the Shortcut  
No. Not really.  If you do see a performance boost by running it shelled, you're probably running your system near it's limits already.
The main benefit I see is that it's just plain cool to turn on your cab and have Big Box do its thing.  
I personally don't use the shell feature because I'm OK with clicking an icon on the task bar.  Also, I'm periodically making changes (emulator or game or writing a new plugin) and need direct access back to LaunchBox or Windows.
 
Hopefully someone else will chime in on this one.  I've never used the Big Box shell feature.

No idea what "SW and MC" and "SW,ESB" are.  If they're arcade machines, check if there's a "SW and MC".ini file or "SW,ESB".ini file.  Of course, replace you acronyms with the ROMs' name. 
Or look for an ini file named after those machines BIOS name or parent system.
If the machines use the same monitor type atypical to most games, look for their monitor type .ini file (vector, raster, lcd...)
Whatever may be in those would override what's in mame.ini.

There's an article in the LaunchBox Strategy Guide regarding the Media Packs.
See here: LaunchBox Media Pack Feature – Version 13.21 - LaunchBox