[Mac OS X] Insert measure keyboard shortcut doesn't exist
There are two issues I'd like to highlight here. One is that, as described at http://musescore.org/en/node/36106#insert, some operations make use of an Ins key. Trouble is, as far as Mac users are concerned, there is no such thing. Interestingly, the Add menu avoids the issue by not giving any shortcut (see first attached screenshot), but in the Preferences it says that that shortcut is assigned to the Ins key (see second screenshot).
Based on the use of the letter B for Append operations (Cmd+B for "Append One Measure" and Shift+Option+B for "Append Measures…"), I changed to Ctrl+B and Shift+Ctrl-B for Insert operations. The problem is that the documentation would get confused because PC keyboards use Ctrl in the same place as Macs use Cmd, so I'm not recommending this, just saying it's what I decided on for my own use. (Then again, I got by just fine without any shortcut at all for years with earlier versions of MuseScore.)
The second issue is the matter of the function keys. MuseScore 1.3 doesn't rely on them; why does 2.0 have to? (Don't answer that. I know: you want to have a shortcut for everything to improve accessibility, and you were running out of keys.) The fact is that on the Mac keyboard all the function keys except F5 and F6 are permanently assigned to specific system-wide actions. You can see in this picture of a Mac keyboard by the little icons on the function keys what those system-wide actions are.
I know with all these things you want to have shortcuts for, it must be insanely frustrating to be told that you can't use a whole set of keys. I do have some suggestions for better shortcuts, if anyone is interested.