Magnetic mask in Apple Motion 6

Do you have an image or clip selected in the Layers selected in the layers list?

The magnetic mask is added to your selected layer.

Not all objects can have magnetic mask applied.

It does not make much sense and does not work for a rectangle, say, only for still or moving images.

I'm still in Moton 5(.4.7) so I sincerely hope somebody who has a more current version will reinforce what I'm about to say:

I've seen videos that explain that the Magnetic Mask must be used with either an image or a video clip. It cannot be used on a Clone of media. I would assume that if it cannot be used on a clone of media, then it would not be available for any other type of object (like text, shapes, etc...)

Check out these videos for more information:

https://www.youtube.com/watch?v=umapCibpegE

https://www.youtube.com/watch?v=GPzjQVgIAKQ