Are you wanting one image to show over another? Movie Edit Pro allows that...

The important thing to remember is that the track sequence is the key. The lower the number track, the more behind or closer to the background it is... similar to a building... each floor represents a layer... the Movie Edit Pro, each track represents a layer.

This is true for doing Picture-in-Picture or Chroma-key effects.

Which then can be used with the effect 'Size/Position' to allow you to resize the track 2 image, and place it where you want it in the overlay... like so:

With Chroma-key, it works much in the same way, but the effect you use is the Chromatic Key color effect..

Once I import these 2 pictures, I can then use the chroma-key effect tools under the tab Effects, then under Chroma Key...

Here is the Mixed image:

Here is the image using Green Box:

As you can see, you do have the ability of layering, but it will depend on the picture. The chroma-key picture I used, I made by cutting out the background around my dog, thus I can apply that image to anything, and it would have a new background.

I hope this is what you were after