Given my db has the following object counts:
72 SYSTEM_TABLE
41 VIEW
3 SQL_TABLE_VALUED_FUNCTION
16 SQL_STORED_PROCEDURE
3 SERVICE_QUEUE
4 SQL_INLINE_TABLE_VALUED_FUNCTION
29 USER_TABLE
7 PRIMARY_KEY_CONSTRAINT
17 INTERNAL_TABLE
5 SQL_SCALAR_FUNCTION
It takes about 10 minutes to expand the list of 29 user tables. The query that produced this list ran for 7 seconds (which is acceptable).
This may be related to the earlier post about not being able to edit ddl in SSDT VS 2015.