Hmm, I’m a bit confused. From the screenshot it appears you managed to select your corner point, didn’t you? In general, we thought it would be best if you first adjust the main corner points (we call them perspective points) and then fine tune with all the inner points. We actually didn’t think anyone would want to move the corner ‘inner’ point, only the corner ‘perspective’ point.
Also, judging from the screenshot, you are using a lot of inner points. It might be possible that you could save yourself a bit of time by following the procedure outlined above: so first adjust the 4 perspective points and then adjust the inner points as needed.
Also, how are you coming along with AutoBlend?
p.s. 3.6.1 is in the final testing steps and it should be out in a few hours or so.