Some tags need to be accessible across solutions while others are specific to solutions. Maybe have a global tag manager.

I use a program called ActiveCampaign, and they have a section to Manage Tags, where you can edit the tags (such as renaming) and see how many times the specific tags are used with the option to click that number and see where they were used.

You can also filter the list and merge tags together (an example may be where two tags were spelled slightly different from each other).