Ideally I want to hit a key combo and start typing the name of a tag while a dialog box shows a list of matching tags I can select from (a bit like the tag box when you ask a question on this site :). Using a mouse makes it quite a bit slower when working through lots of photos ...
And I am aware that in digikam 2.x I can apply a keyboard shortcut to a single tag, but that doesn't really do what I want. It just applies that tag to the currently selected photos - I can't just type and search in the subfolders.