Database documentation is as paramount as it gets in terms of database development.
SSDT should include a robust diagram experience with the ability to comment tables and fields.
I agree, and actually diagrams should be in both places, ssms and vs
I agree. If diagrams are being removed from SSMS because diagrams are a "developer thing," then moving it to SSDT in the developer's Visual Studio tool makes a lot of sense.
I would like any new tool to read & write existing sys.diagrams data. I have hundreds of diagrams in dozens of database per my organization's documentation policy. I really like the existing diagrams being connected to the database so that column changes in tables do not require someone to manually refresh the diagrams to keep them up to date.
If we don't get something that can, at least, present sys.diagrams-based diagrams, then upgrading to SQL Server 2019 will result in Microsoft capriciously throwing away all that documentation I have generated over the last 16 years.