So, this may not necessariy be asking for help as much as a feature request, but regardless I'll ask in case there is a solution.
Basically, I use CEMU emulator, and I have multiple save folders on my computer for multiple users. I load each of these with a command line argument in cemu. Launchbox's additional apps feature doesn't allow for command line arguments when you check "use emulator" so I have to type the full path of the emulator as well as the arguments I want to use (not exactly the intended use of additional apps but it works).
This works fine, except for one thing- the "escape" shortcut to close the emulator that I set through launchbox in the emulator settings doesn't work (presumably since I'm not loading the emulator like launchbox wants me to.)
I hope I've made this clear enough, but I can provide more details or screenshots on request.
So in short: additional apps doesn't support extra command line arguments while "use emulator" box is checked.