The ErgoDash[1] has 7 keys along the bottom, of which either 3 or 4 are thumb keys (the 4th key can be soldered in two positions).
At least the way I set up my ErgoDash, either side can be primary. I think this is now standard.
> I find it hard to come up with uses for the fancier things the keyboard firmware can do (eg dual purpose modifier keys, space cadet shift, macros etc).
- I have[2] a simultaneous press of T and 5 set to be F5. Similarly for the whole top row.
- A short tap of my media key is "Media Next". A solid press is "Media Play/Pause". A long press is "Ctrl + Media Stop", which my media player recognizes as "Stop after current track". Something similar for the volume key.
- Enter is a thumb key, but when held down it's Ctrl.
- I have a window switching key, which holds down Alt and presses Tab, but keeps Alt held down for 0.5s in case of subsequent presses.
- I have single keys for Ctrl+PgUp and Ctrl+PgDown, which switches tabs in many applications.
[1] https://github.com/omkbd/ErgoDash
[2] http://www.keyboard-layout-editor.com/#/gists/501437fce9123e...
