Thanks for your response! I did stack the video clips up but found I had to use the overlay composite mode to get the effect that I wanted. I could also change opacity to see the bottom layer.
However, I created a new problem with one of the areas in my sequence where I was trying different effects. One of the clips that I used and then rendered with others and finally deleted continues to appear. A green line appears on the render bar, and even without any clip in the video tracks at all, the original image remains. If I put other images in that area of the timeline, the original (missing) video picutre overlays over the new clip. This is happening to one area of the timeline only, so I can’t use this sequence, Is there a way to break the connection with this clip? I don’t mind starting a new sequence now, but I would like to learn to correct the problem in case it occurs again after I have created a sequence I want to save rather than one where I am practicing.
Susan