Reply To: Wanted: shortcut for ‘select all unused’

Wow, that is strange. I did a quick search and found an old Adobe forum post where Dave Saunders and a few others had written some scripts that might be of use. The post is a few years old, but I would say the (Javascript) scripts would still be worth a try.

https://forums.adobe.com/message/1106498

I tried the script posted by Kasyan Servetsky (post 16 from Jun 23, 2010) in CC and it worked with no issues, given doesnt really select them it just deletes the unused. So hopefully one of the scripts posted on that page should (hopefully) work and you will then have something to assign a KBSC to.