Adding/removing a tag does not update immediately

Tested with MacOS.

Test steps:
1. Go to layer properties -> Variant Tags
2. Add a group
3. Add a tag
-> The tag does not appear next to the group. The view has to be refreshed e.g. by re-selecting the layer.
4. Remove a tag
-> The tag does not disappear. The view has to be refreshed e.g. by re-selecting the layer.

This gives user an impression that the tags are not working properly.