There should be a context menu item in Dolphin where a user can: Click on three items: 'Tags', 'Remove all tags', 'Add tags'. Clicking 'tags' will display a list of tags, which can be individually removed. Expected: Mary clicks to open a context menu on a file. She expects to see a 'remove tags' or 'add tags' option. Actual: The only way to manage tags is by a) selecting a file (or folder) or multiple, b) clicking on 'Tags' 'Change'. The problem is that most users have one click to open a file, or right click to amend it. Thus clicking the + to select a file and then clicking tag is unintuitive to many and doesn't follow the standard workflow in similar apps.
Resolved (kind of) in KDE Apps 19.04 whereby a tag menu is provided enabling viewing, adding, removing, and creating of tags relating to a file/folder. It doesn't have remove-all, which might be nice, perhaps for a separate bug.