MM's already pointed out the option to change main FFF button behavior., but here are a couple other ideas:
- You can click one book, then Ctrl-click it to unselect and then have none selected.
- I have the 0 keyboard key mapped to 'Add new from URLs' and the 1 key mapped to 'Update Existing', etc. See attached.
- Also, I have <spacebar> mapped to my preferred View Manager(PI) view, that also clears selected.