Looking good, though I get this error when trying to choose an icon image not available in the current listing:
If I choose an icon that has been used before, i. e., already listed in the chains dialog, all goes well. Also, I've noticed that a conflicting setting that I had disabled from JS+ plugin doesn't affect icon displaying anymore. I re-enabled that setting just to see if that new icon combo location had any positive effect on that. It has! However, the error I mentioned had happened before I re-enabled temporarily that setting.
I haven't tested yet the new feature to run actions as jobs.
This on Windows 10 21H1, Calibre 7.7