I was testing some of the blue tree slottables last night and ran into the following issue. When I'm changing just one slottable, there's no real problem. If I'd like to change two, however, once I've changed the first one, the slottable that was up in the bar is now stuck to my cursor, and I can't pick up the second new slottable without confirming the first selection. This is similar to what happens when changing active skills, but because there's a 30s cooldown on slottable changes, the process becomes quite slow. A more minor annoyance is that when a slottable is stuck on the cursor, although I can assign cp to stars with the +/- buttons, the tooltips don't show so this assignment is blind.
Is there a key combination I'm not aware of that drops skills/slottables from the cursor? I'm on PC with mouse/KB but if this is also an issue in gamepad UI then answers there would be useful to others.