It used to be possible to edit/remove and save tags in files listed in the left side pane in v2.3.2 (just tested it again on a different computer), but since the v2.4.1 upgrade, this no longer works.  It displays a no-entry sign next to files when saving.  It does remember the changes once the files are linked to releases and in the right hand side panel (unless the data is replaced with information from the release) and saves/removes the tags correctly, even though the files continue to display the no-entry sign (when linked to a release) until it's saved.