This is worth a shot. I use a lot of nested tags to organise notes and docs. In an app like Drafts, adding a tag which is nested using the forward-slash ‘/’ appropriately shows the nested options, and narrows them down as you keep typing. Other apps also mirror this behaviour (Bear, I believe?). As I want to use DEVONthink for everything (endless app proliferation, anyone?) I’d love to see a bit more nested-tag love given to the DT UI.
Thank you for the suggestion, noted.
As an aside: Have you read the Getting Started > Tagging > Nested Tags section of the built-in Help and manual?