user-defined Data types
User-Defined Table Types are not searchable.
Karis Brummitt commented
Add User-defined Table Types. They did not appear in the list at all. In my case they should have appeared in the stored procedure and the definition of the user-defined Table type as well.
Now that UDTs are usable as READONLY Stored Procedure parameter types, please add them. I know MY databases, but I sometimes forget where a Type is used... Group under "Other" perhaps in the object type dropdown?