Generally, transformation output tables are deleted upon the end of the job processing(that is at the en of the SAS session running the job). There is no silver bullet approach to remove intermediate WORK tables. Some transformations remove intermediate tables used within the transformation (tables that are not visible in the process designer).
What you are asking for is some automatic way top delete tables that are not longer to any use further on in the job I guess it would be some messy logic for DI Studio to figure that out, including user written code/transformations.
So, you can do some user written transformation that deletes those tables at proper locations (not so nice from a process design view), and insert a clean-up routine in the post process (in case you're WORK is a permanent storage or if you run several jobs within the same session).
Another possibility is to use VIEWS as transformation output when it's possible.
What is your concern, running out of temporary disk space? You can also build shorter jobs, which will automatically delete temporary tables at the job end.
/Linus
Data never sleeps