I'm an long time Twiddler (ver.1,, ver.2, and now ver. 3) I killed more version 2 than I can remember both PS2 and USB, just wore them out.
Thumb buttons have always been hard for me in chords, such as capitalizing first letter of words.
What I think would be of great use is being able to press/release a thumb key or combo of thumb keys and have that then modify only the next chord typed.
I've tried the "sticky" function but that is like pressing caps lock and not what I had in mind.
Press/Release shift, R000 = A instead of a
Press hold shift, R000, release shift = A (will work as normal and not modify the second chord typed)
Press/release shift, press/release ctrl, R000 = Shift+Ctrl+a
I figure we'd also need a dummy chord to cancel these modifiers if you hit one by mistake.