I've seen this kind of thing in a different programme, but I think the way they do it is make all of the combinations of elements before hand and make them unselectable (only start with like 10-14 elements) then when you combine them, it uses the certain element combination that it has saved (any combination that doesn't exist just comes out as 'null')
This probably wouldn't be possible with TPT - there are jsut too many combinations and it would probably lag.
You can't just magically stuff programs together like that. It's like trying to merge a cow with an elephant, you don't get one bigger, more effective creature. You get an explosion of gore and messyness. D: