I thought I would check into tagging some of my document files by topic; home, work, finance, etc. But I can't really see any functionality for the tagging option. If I enable the information pane in Dolphin, I can click on "add tag" and open dialog to a create a new tag ("Home" for example) for a file. But if I then click on the new tag in the information pane I get an error that says; "The file or folder tags:Home does not exist.". I can't find any way to search for or sort by tags and they are not mentioned in the handbook other than to say they exist.

Do file tags have an actual function?

Earlier KDE Forums: Tag files and search tags - viewtopic.php?f=67&t=141100

With the Dolphin 19.04:
The Bug 182367 - By default, no way to browse tags assigned in Dolphin (maybe show "tags:/" KIOSlave as a Bookmark by default) - https://bugs.kde.org/show_bug.cgi?id=182367 has been fixed with the 'Show list of tags in PlacesView' - https://phabricator.kde.org/D7700