cannot combine manual and auto track

HI, i created a track and do auto track, then at some point it stops, in other app , ussually i can just drag manually the tracker to continue frame by frame manually. But in blender i can’t drag that tracker that has been in auto mode, the corner handle is dissapeared so looks like it’s locked , but it’s not locked actually. Any idea what happen? is it possible.

Also, the opposite workflow, if i start track by manually moving it then i can’t do auto track to continue from the last keyframe i made. why is it ? this is so weird.

is this a bug ???