chdkptp is the best way to capture screen shots in all modes.
Never used it, so will need time to see how to use it.
FWIW, aside from screenshots, you may find it useful for script development, since you can interactively run camera-side Lua from your PC. I tend to find this much more productive than editing scripts and copying them to the card (but I may be biased
). Uploading scripts without pulling the card is also convenient.
The screen dump module from
https://chdk.setepontos.com/index.php?topic=14342.msg146135#msg146135 could also be used. That gives a full capture of the various buffers, and with the current svn chdkptp, images from an lvdump captured with that using something like
lvdumpimg -infile=whatever.lvdump -vp -bm
Or just replay it in the GUI.
I think I figured out how to make that module less of a mess in the core, so I'll probably refactor it and add to the trunk at some point.