I'm able to do this in Illustrator but I am trying to figure out how to do this in InDesign.
In InDesign - After I have created a custom shape (clipping mask) with the pen tool I drop an image inside the shape (CMD+D).
However, I would like to add other shapes or images into this clipping mask and adjust the blending options. How do I accomplish this in InDesign?
Thanks Willi for your detailed instructions. That is pretty much what I wanted to do.