If you just want to select and move vertices or handles the best workflow is to expand the timeline, select the path you want to edit in the timeline, select the Selection Tool (v) and then pay close attention to the cursor. If it is a white arrow with no tail, you can draw a selection around one or more mask points, when the no tail arrow turns black you can select the point, handle, or path segment you are hovering over and drag that around. When the cursor has a tail and looks normal, you have lost the path and are now only able to select the layer.
If you need to modify points, or add them, or use the feathering tool goes back to the pen tool by pressing "g" and once again pay attention to the cursor. It will change as you move over the path, over a point, or over a handle. You can also use the Alt/Option key with the pen tool to temporarily change the pen tool to the convert vertex, or tension tool if you are using rotobezier curves. The Ctrl/Cmnd key with the Pen tool gives you the same cursor behavior as using the selection tool with the path selected in the timeline.
Here's a quick overview of the proper use of the pen tool I did a long time ago. Maybe that will help. It just goes over the use of the pen tool:
Thanks again, but i am searching for something else. The selection tool with shift activated comes fairly close to the first thing i am looking for, but if you make a big selection over maskpoints twice with shift it deselects some maskpoints that were selected twice instead of only adding maskpoints to the selection.
Since you asked for it, here's a pro tip/ hint: Use Illustrator! If you really want that kind of mask editing, AE is simply the wrong tool. AI would be much more adequate as a) its image trace tools offer better options to begin with and b) of course you have a whole toolset to slice and dice vector paths, which c) can then easily be imported or copy&pasted to AE. Really no point in making your life difficult. Even if you include some utility scripts found on AEScripts.com, AE will never even come close to these possibilities.
Thanks for the reply, but both programs together are too expensive for me. Especially since it feels really forced, because sometimes i see no reason why After Effects is designed so frustrating in exactly this regards. There is not even a classic fast paint filltool! Or if you draw with pen in AE it is really difficult and slow to start a new mask without closing the old one. And vectors or something existed in the past i think and got removed? But it is still a nice program!