Can I manually adjust a Plane Track? I use 4 points to create a plane track.
It works for half of the clip but at a point the movements are difficult to track and the plane starts to wobble.
I would like to manually correct the plane movement, on a frame by frame basis, a bit like it works for masking.
Unfortunately, anytime I move a corner of the plane, on a specific frame, it readjust the position of the plane for the whole clip.  

Is there a way to take manual control over the plane track ?
In Blender 2.9+ there is an option for Auto Keyframing plane track corners.
If you press N while in the tracking scene and open the Track tab, there is a dropdown for the Plane Track which allows you to set Auto Keyframes for plane track corners.
You can make manual adjustments without having to export the trackers to empties and hook them.