I have a video rendered from a 3d software of a book opening up. I want to track the first page and add content to it. The thing is when I try to track the entire page in mocha it gets screwed up at the beginning when the book cover is hiding most of it, and at the end when the camera is moving into the book. I'm not a real mocha expert (I have only mocha AE) but I think If I could combine 2 tracks (creating a first track, delete the badly tracked frames somehow, and parent it to another track) then it would work. I don't know how to do it, though.
In general, the approach to take in mocha is to track until the track loses it, then go back a few frames to just before it loses it and move your search area to a more appropriate area. Keep tracking.
Also - the AdjustTrack module is designed to help correct tracks that drift.
Lastly if you wanted to combine tracks you could try duplicating the object and using have from beginning and half from end and delete the unused keyframes, but I would not recommend this technique.