Hi there: For me it would be very helpful being able to create a bundle tag directly in the tagger. I tag my mails by customer (top hierarchy) and then by the different projects (sub-hierarchy).
Each time there is a new project to tag I have to navigate to configuration and bundle the tags there.

Suggestions:
- using a "+" between to tags in the tagger should create a new sub-hierarchy tag
- drag&drop functionality fur bundling should also be available in the tag filter