I would like to insert a new picture into my movie.  (MM 2012) I have not yet been able to make the split function active, if that is indeed the way to do this.

I have been able to reduce a picture of 10 seconds duration to 5 seconds, and then add a new picture of five seconds duration.

This leaves my narration and background music in the proper places relative to the pictures, but the captions slide "forward" in the timeline and it seems I would have to move each one of them back manually.  Is there a way to slide the whole group back to the proper location?  I tried adding a caption to the new picture, but that doesn't seem to help.