Swapping images in Adobe Express

When using images from the Media panel it is certainly possible to drag and drop. I managed it by selecting the image on the canvas, opening the media panel and dragging a different image onto the top of the current image which was then replaced, keeping the size. 

Using images I need to upload from my computer I selected the current image, clicked the Replace image icon in the left-hand panel, navigated to my image and clicked upload. This again replaced the current image with the new one in the same size. 

Swapping one image for another within the new Grids feature doesn't work - and I expect that feature is the one you are missing? Was it in the previous Collage feature, which we don't currently have, or did you create your own collage template?

Whilst I can see the usefulness of being able to quickly drag and drop images over one another to swap them out, I can also see it being a bit awkward with accidentally swapping out images with each other when not intending to. I've done that myself without meaning to when selecting images from the media panel to use and it's a bit frustrating.