Tbh, This Is A Bit Much To Ask But I Think You Should Add A Button To Either Send Rounds, And/Or A Button To Fill The Map With The Selected Tower. Again, This Is A Lot To Ask Taking This Is Made In SCRATCH Of All Things, So I'd Be Very Surprised If You Said Yes.
So is the first thing your suggesting races?
The second thing would not be too hard, I think it could be if I were to make it place the maximum number rather than filling (which wouldn't be far off the max). I can try adding this first to sandbox and then other game modes along with other stuff like how btd6 sandbox has clear all bloons, reset abilities etc.