How I did my Zipline:
I first flew Inspire to where I wanted point A then hit the "Set with aircraft position" for A, Then I flew to the B position I wanted and hit the "Set with aircraft position" for B. (I am now hovering at B point) Then I set location A at 90 ft and location B at the lowest I could go which I think was 16 feet. Then I set Positon to 0% (Which will send it to A when I engage) (remember I am still hovering at B), Then I set speed to 25%, now I engaged and away she (or he) went towards A. If you want to go back to B now just disengage and go back to your position slider and put it at 100% which would make it go to B after you engage again. The Position/Speed slider is near the bottom of the app.
One thing to note is the Inspire can only descend at 4 meters/sec so if you are really high on one point and really low on the other and the distance between them is short, it will not have enough time maybe to get that low in the short distance.