Re what's new in 2.1, I think I committed "menu collation" between 2.0 and 2.1, so that counts as a new feature, too. Menu collation, unless disabled in KUAL.cfg, groups separate json menus that share the same top menu name under - you guessed it - that top menu name. In adding this feature I thought we could define a common top menu structure, i.e., System, Network, Games, etc. and button developers could graft their buttons under the most pertinent entry, for instance, the firewall button under Network, etc. Sort of like the linux system menu categories. That's just and idea. I used menu collation to add extra KUAL features under the KUAL menu entry, things like setting sorting modes, replacing the store button on KT, and more.
The button package is attached to this post. Unzip it in /mnt/us on your kindle. You only need the KUAL-add-ons folder. See also this other post