Okay, fear my crazy Inkscape skills
Anyway, after a lot of pondering, the only likely case I can see where you’d do another action on the same selection is to remove things from tag “A” and add it to tag “B”. So I’d get rid of this pre-selection idea and instead offer a tag replacement mode.
To make it a bit more streamlined, I’d present the operation mode on top (because changing it also slightly modifies the UI below) and for tagging, moving stuff from one side to the other takes immediate action.
Deletion would stay pretty much the same though, instead of the tag dropdown on the right there would be a fat “Delete” button and the resource view would be labeled “Resources to be deleted:”
I’m not sure if the tag replacement mode is really that practical. It would have to remove the “All” and “All Untagged” meta tag choices on the left, and also hide all resources that have both selected tags I guess.
Oh and the tab names describe more the use case rather the way they present data, but I don’t feel like it’s the ultimate choice yet…
totally forgot, that edit button is to add/rename/delete tags, in a popup menu if that makes sense. Or would you rather have a more sophisticated dialog to manage tags themselves?