Is there a way in Movie Studio to set a video to semi-transparent in one video track and play another video or still images over the transparent video so it plays in the background?
Put the clip that you want semi-transparent on the Video Overlay track and whatever else you want (other clip, images) on the Video track. Grab the top of the Video Overlay track and you will see a blue line with "Opacity is 100%" written there. Slide the blue line down and you'll see the opacity change. Play with the opacity value until you get your desired result.
Under Help --> Search, enter the word Opacity, and you'll see a picture of what I'm getting at.