Pressing the “Edit Collider” button in the Polygon Collider 2D should make it possible to grab the points and move them around in the scene view; it worked, it no longer does, at least in my projec.
I can still modify the bounds by changing the values of the points in the Points Path Elements array though. Fortunately.
I checked, it works for me. I can grab the points and move them around. Maybe you could try on a physics2D forum, as the Polygon Collider 2D component is not part of Cinemachine.