You can add any emulator you like, just type it into the box like you did in your bottom image. Then go to the associated platform tab and type in the platform the emulator is to be used with. That is what that error message is, you didnt specify what platform the emulator is to be used for.
EDIT:
You add emulators via Tools/Manage Emulators.
When the new framework was implemented (which was called LaunchboxNext while in beta but is now just Launchbox) the options were separated out somewhat. Nothing has changed it's just the tree that looks different as there were so many options in the program now that they needed organising a little better. All the old options are still there, just under the legacy tab, and newer options that were not available in the old framework are separated out from the legacy ones.
Yeah as both you and i said Launchbox doesnt know which file to load when there is more than one file in a archive. Thats why i suggested unzipping them, then you would just import the .gdi files into Launchbox, so then the correct file will be passed to the emulator.
It is not possible to specify the file to load coming from a archive. Your best bet would be to extract them or convert them to another format that whatever core you are using supports.
There is only one staff, and thats the dev himself. Can you pull a log of this happening? Just go to Tools/Options/Debugging and turn it on, then use it the way you have been where you get the crash and post the log from Launchbox/Logs.
Thanks.
As @DOS76 said you can name the platform whatever you like, so just make sure you add what you called it to the associated platform tab of the emulator you are using.
While i have no idea what most of that log actually means, i do see references to the pcsx2 configurator plugin in it on several occasions. You could try moving that out of the plugins folder and see if there is any change.
Im sure he had his reasons, likely to do with player numbers, or just updated versions. Also the parent may be in Japanese and maybe he chose the English language versions, which are technically clones of the Japanese parent in some cases.
In Launchbox go to Tools/Manage emulators and double click your retroarch entry. Click the Associated platform tab scroll to the bottom empty box and type in the name of the system, it needs to EXACTLY match what you called it in Launchbox. Then double click the core box next to it and choose the core from the dropdown.
It should look somewhat like this.
That is a old tutorial and Retroarch has changed the buttons now, its enter and backspace for select and back. You need to go to online updater/core updater and click on the core you want, i recommend genesis plus gx.
OK have you actually downloaded the core you want to use? Retroarch calls there emulators "cores" and it doesnt come with any, you need to download them from the retroarch UI.