can you subtract any union dues? For instance, SAG union?

W-2 employees cannot deduct job-related expenses on a federal return.  Job-related expenses were eliminated as a federal deduction for W-2 employees by the tax laws that changed for 2018 and beyond. 

But you mentioned SAG----Screen Actors Guild?   If you are a qualified performing artist your union dues can be entered for a deduction on a federal return.

Your state tax laws might be different in AL, AR, CA, HI, MN, NY or PA.

If you live in a state that lets you deduct job-related expenses, the information will flow from your federal return  to the state return, so enter it in Federal>Deductions and Credits>Employment Expenses>Job-Related Expenses