motion tracking improvements (add your own suggestions too)

option to only show tracking markers between certain frames (disabled included). will make it possible to easily select trackers of problematic areas when for example you have overlapping trackers.

remove close tracking markers, leaving only the one with the lowest error.

when using detect features, and specifying the closest allowable distance between markers, have that also take into consideration the existing markers on the screen. Maybe a bug that it doesn't already? Otherwise you end up with markers being created close to existing ones, which causes problems with solving the camera.

have the tracking forward/backwards and solving only calculate in the timeline preview range (if one is set). So that you can refine problematic sections without damaging the good sections. Faster too.

limit clean operations to selected markers only.