A long-standing annoyance with Qt Creator is that some standard text editor keys (cmd + up/down) do not work.

cmd + up = Go to the first line of the document (position the cursor at the start of the line).
cmd + down = Go to the last line of the document (position the cursor at the end of the line).

These standard keys work in pretty much any text control and have done so since the Mac OS 9 days.