Mask modifiers in Blender's VSE

Hi folks. I recently finished a 3 part mini series exploring the use of regular strips as Mask Modifiers. Topics include hiding/showing content and creating transitions. Links: youtu.be/UjABo1WLEbE
youtu.be/iG8qTf67ov8
youtu.be/tGYXXxZfxAE

And as a "bonus", I just uploaded a video showing a transition done with normal animations: youtu.be/gP_Udtt72zo