To key-bind in Bartender4:
Q: Where are my keybindings? And how do i bind new keys?
A: Bartender4 buttons do not automatically inherit keybindings from the Blizzard bars (except for Bar 1), you have to use the new KeyBound to re-bind your keys. You can access KeyBound by its slash command (/kb) or through the button in the BT4 config. Hover a button, press key → voila!
From the Bartender4 page here at WoWInterface.
