I can't seem to be able to save my keybindings so they persist outside of the current play session. I found that the "Apply" button was visible prior to and while I was in the state for choosing a keybinding, but after choosing one it was always hidden. This just seems like a minor state issue with showing the "Apply" button. 

Yeah we are aware of the keybinds not persisting over multiple play sessions currently. We're releasing patch 2.7 soon but I don't think that fix will make it in in time. It will be a high priority for 2.71 though. 

Patch 2.7 released today and we were able to fix the keybindings not saving outside of your current session. It should have been saving by default even with Apply disappearing, but if a keybind was placed onto your Mouse it wasn't correctly saved.