As a guitar amp designer, I bought this app as a way to prototype circuits without having to used an over-complicated program like Eagle. The common vacuum tube types (for starters) are 12AX7, 12AT7, EL84, 6V6, 6L6, and EL34. Unfortunately I don't see any options for even a generic tube which you could input operational values. If that is too complex of an undertaking, maybe just explicitly define the above tubes, after all, they are the most common tubes being used in amp design (and has been for decades). Hoping you can implement this!