DT3 Custom Metadata - "Categories"

As a user of DT3 for some time I am still mystified why custom metadata is a global setting and not specific to a particular database. For example, I may want custom “category” and “sub-category” metadata items for two unrelated databases but the items within the categories and subcategories would be completely different. Let’s say I had two databases - one for books, and one for accounts. My books database might use a custom metadata item called “category” with entries such as “Fiction”, “Biography”,“Historical” etc and my Accounts database might need a “category” metadata item with entries such as “Invoice”, “Receipt”, “Refunds” etc. Both are categories but are relevant to the items collected within the specific database.
If one has many databases, as I have, what is the point of having global “custom” metadata items? - or am I missing something?

A global setup ensures that there won’t be any inconsistencies/incompatibilities when moving items between databases (or between devices as the setup is synchronized by default). However, a future release will include the possibility to show in each database only the desired custom metadata.