Jason, you're a star!
The custom config is definitely the right track, I think.
Big 'however' though, is that any commands run in there are entered before the image is mounted. (see image below)
I'd have no problems removing the CUE from LaunchBox's Mounts (in the game) and just copy the IMGMOUNT command shown, before the attempts to CD directorys, in the image.
But I've been keeping everything on my OneDrive (gotta fill that free 1TB of space somehow!) so I can have my games synced on my PC and my Laptop.
I'm not sure if the path will work with just IMGMOUNT D "..\Games\MS-DOS\etc.cue" so I don't have to have set drive letters?
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Ctrl+F4 = Changes disc image in DosBox apparently <3
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Thanks SO much for your continued help and such an AWESOME application!