Welcome back to Toad World! This sounds like a great feature enhancement. I have created a task QAT-1885 for future consideration for official support.
However, I discovered an interesting workaround which imports .TSM files into Toad Data Point. Give this a try and see if it can be accommodated to fit your needs
In Toad Data Point (3.4), select “VIEW -> Project Manager”
(Optional) Create a new Project
Drag and Drop your existing .TSM files into a project of your choice.
Open the Query Builder
Drag and Drop one .tsm file into the Query Builder. It will manifest itself as a subquery.
Drag and Drop another .tsm file into the Query Builder. It will manifest itself as 2 subqueries, though they are actually duplicates and changes sync with each other. Note that the Query Builder will prompt to close; simply push CANCEL to continue.
Modify the Subqueries as you wish, and ensure you Select something in the Parent Query
Select Execute SQL to perform the SQL
Double check the SQL that was created by looking at the Messages Tab.
Note that closing the Query Builder window may make a Toad Data Point Error Message appear.