After finding the info on how to resize an imported video (Level Settings) - It was easy to select the whole column and resize the frames. But when I clicked on Save All (having seen the advice over and over to only use "save all" as opposed to "save scene") - the error message came up:
Failed to save the following resource: X.mp4
So, there's a different way to resize an imported video? A method that the program won't reject?