Is there a way to convert selected tags to groups?
Thanks.
Tags, technically, are Groups.
They could be converted by right-clicking and choosing Exclude from Tagging, but what are you thinking of doing?
I just discovered the way to do it:
Select the tag in the database column (three-panes view), choose Move to from the context menu, and choose the group you want to put the new group under.
Does exactly what I want.
Thanks.
Glad you did what you wanted but I’m still curious as to what you’re up to. 
Okay. I am just getting started with DTP. I imported a bunch of bookmarks from Pinboard with a bunch of tags. I’m thinking that organizing by groups is better for my working style. So rather than creating groups, moving bookmarks, removing their tags and then deleting the tags themselves, changing a tag to a group is much easier. Does this answer your question?
By the way, “moving” a tag to a group is at least semi-intuitive. Making a tag into a group by excluding it from tagging (if indeed that’s what happens) is not intuitive at all.
It’s intuitive if you understand that, in DEVONthink, tags are a special kind of group, and that groups can become a special kind of tag (colored differently than normal tags).
By default in Database Properties groups are excluded from tagging. Change that, and groups become tags.
Move a tag outside the Tags cluster and it becomes a group.
Groups are the organization locations of documents. Tags are attributes of documents.
Hope that helps.