VSDC: make transition treat the video and the background image together as a unit

I used VSDC to apply chroma key (i.e. make the green screen transparent) to a video and placed a background image on the layer below the video. Now I would like to apply a transition, such as "Page turn". Of course, I want the transition to treat the video and the background together as a unit, not each one disappear on its own (i.e. one page turn, not two page turns). How can I achieve this?