I already submitted these to NCH directly but would like to discuss them here as well to stimulate other ideas.
My suggestions were these:
1. Add a Scene Window that would show you thumbnails of the compositions. Allowing you to quickly, and visually, change from one composition to another. They would have a thumbnail snapshot of that composition. You could drag and drop them to reorder them. For people coming from presentation software, this would be a very familiar interface. You might also see the entire timeline below showing Scenes/Compositions represented there instead of the layers?
2. Add a Toolbar on the right to select between Objects (and perhaps some high level categories of objects), Text, Effects, Audio/Music and more. Once one is selected you then get a visual selector for the graphics, music, etc. This window could be used to replace the current New Object dropdown - which requires too many clicks to find the clipart you want. It's far more intuitive and easier to navigate.
3. Puppet Warp. If you've seen this in Photoshop you know what it is. You use this to animate a warp/deform of an object/layer. You put dots on the object/layer image and then when you move them and place animation points you get movement. Could be used to make a character walk, dance, move anything. See here - https://www.youtube.com/watch?v=lIYxyQ2s64c
4. New idea - as well as NCH's own clipart library - why not build in a visual selector for GIPHY's Sticker images? They've got thousands of images that would be amazing for ExpressAnimate. Check these out - https://giphy.com/studiosoriginalstickers
Here's a quick mockup I put together with these ideas. https://imgur.com/d88BjIk