Many users reported that they are not able to delete unknown login items on their mac. The user just updated to 10.13 and their Login Items window in Systems Preferences is filled with ‘Unknowns.’
Just delete the file name called backgrounditems.btm
search out and destroy a file called backgrounditems.btm then reboot. The login panel should be cleared out. The senior advisor and I rebooted three times with a test app inserted through the normal login panel procedures and all was well. I added back my normal items and they’re still working just fine.
If you add back your normal items and they’re still working just fine.
This is the best known method to fix the problem “Can’t remove ‘unknown login items’?”.