Here's the answer I got from Trolltech support.

I've created tasks for the developers about these issues.

http://www.trolltech.com/developer/t...9&method=entry
http://www.trolltech.com/developer/t...0&method=entry

You can combine code and designer easily enough. E.g. design all your
widgets/actions etc in designer.

The set your own icon and shortcut in code on the actions in code.

(the links don't work for me, but basically it's not possible yet).