I have indeed other entries in the registry, under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers:
000TabblesOverlayHandler… (2 of them)
0GenieTimeLine-… (5 of them)
Too bad it is not possible to combine overlay icons, but understandable. It would become very crowded if all apps would add their own overlay icons to the same file.
As an alternative, would it be possible to display the information whether a file is tagged in an additional column displaying in Windows Explorer?