Reimplement ERD Diagrams in (SSMS18)
ERD Diagrams are basically needed to check the structure (visual) of a database. it was a key component of SSMS. Why would you even remove it and force us to install another 3rd party app, while SSMS is already a bloatware on itself...
Database Diagrams are back in SSMS 18.1.
With Office 365, if you let your paid subscription expire, Microsoft lets you continue to operate the applications in read-only mode to view the documents that you created while you were a paid subscriber.
With SQL Server 2000 through SQL Server 2017, I have created hundreds of diagrams in dozens of databases as part of my organization's database documentation policy. With Microsoft discontinuing diagram support with SQL Server 2019/SSMS 18, Microsoft is essentially throwing away all my documentation without my consent.
Please seriously consider implementing a documentation-only mode for database diagrams (as I have posted in "SSMS 2018 Database Diagrams - Display Only" https://feedback.azure.com/forums/908035-sql-server/suggestions/37442596-ssms-2018-database-diagrams-display-only ).