When adding Media with included Cover and lots of Metadata it would be nice to see unassigned elements (Filter Option) to identify the elements that needs manual assignment.
Have you tried this plugin?
No. Have not looked at Plugins so far… unfortunately it is discontinued since 2014…
This (and its sibling, which does the opposite) are now part of WebTools.
Early 2021 clean-up: implemented (filter by unmatched)
