So the name of the export slice preset (Default) or Scene is what determines the filename. I figured that out from testing different scenarios. But here's where I'm stuck. I can either select individual layouts and they export to their own files, OR I can export individual scenes to their own files. But only one or the other.
In other words, if I have 2 scenes, with 3 layouts each, I would want to be able get 6 different exports.
And wouldn't you know, in making screenshot examples for this post it suddenly started working as I would expect. Before it was only showing me three layouts in the export menu.
After some testing, I'm willing to bet it was because I had the same layout names in both scenes! That means they weren't unique, and Hype doesn't have an option to prepend the scene name. The last example is how I typically would organize them. That would be a handy check box to have.