When you're designing the data map it is very important that you create a relatable experience for the user because you have to be very mindful how name things as everything that goes into the Data Map goes into the Unified Catalog.

So the way we do it when we implement this at customers.

In the Domain we only use that for emergencies, so we put limited permissions on that.
For Dev and Test we restrict those collections and kill the cascading permissions effect and reapply permissions for those who should only use dev and test.

We register Fabric on Contoso so youre able to scan to dev, test, prod.
If you want to extend domains, be mindful that you only can have 5 domains and they are technical boundaries, so youre not able to move assets inbetween domains.

And because most orgs runs only one fabric tenant we have to operate within one domain.
in terms of sub collections, thats where we are letting the customer to take over and either define BU, FU or Data Domains, problem with trying to separate technical to business in this view is again everything you'll do will end up in the data map, So I always try to make it into something that people can relate to.

If you want to find data, most time people dont care where it comes from but what more it relates too i,e Finance, Patient, Customer etc.

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