Hi,
due you know if rename tag names in database could break something ?
In fact I have to many tags to rename them manually, and I want to rename all of them directly in the database.
Best
wouldn’t it work to rename them in a journey?
No it is not possible 
I would think you could either use campaign to rename the tags or do a CVS import to merge those contact with new tags and then do a campaign to remove old tag on those with the new tags.