I use bookmarklets for all my posting and hardly ever enter the MT interface to do anything other than edit old posts. So if you are like me you will need to modify bm_entry.tmpl instead of edit_entry.tmpl, but otherwise this is what you need to do if you were using Scott Andrew’s PowerLinks in your MoveableType blog and they all got lost when you upgraded: Custom Tag Buttons in Edit Entry screen
If you want the new edit entry template that came with the 2.6 release of MT don’t upload the edit_entry.tmpl that comes with Scott Andrew’s PowerLinks. You will need to edit the template file yourself.
Aside from that these things are great!