How I got my own custom screenshots to work like a breeze.

[PedgeJameson]

In Launchbox go to:

Tools>Options>Screen Capture

Set it for F8

This is the same key for screen capture as Retroarch, but doing it this way there will not be any conflicts I have experienced before.

Note: there will be a slight delay, so make sure there is some action going on, or you may end up with something stupid like "Next Stage Now Loading".

When you quit Retroarch, LB will ask if you want to save them, just confirm, all set.