Dysfunkt

... then use pitch bend to make the slide tool? Does everything the program does have to stick to midi cc?

Oh yeah, and a slider in the middle to say how slow/fast the curve should be

So as far as I've seen nobody has done this yet even though to me it seems fairly obvious. In order to denote a slide there should be a tool the lets you click on any given note to add a slide. Then you could simply drag the end of the note on the y axis and the other end of the slide (like a selection tool) on the x axis to set where it begins. Seems to me like this would be the simplest way to do a trombone properly