Does anyone know of a tutorial or other guide to editing animated GIFs in Photoshop Elements?

I’m using PSE 18. With all this extra time on my hand and little in the way of photo-taking opportunities, I’ve been experimenting. I used online tools to create a couple of GIFs (one by converting an MP4, the other by uploading a group of photos), and then tried using Photoshop Elements 18 to edit them. Clearly, this is not a robust PSE feature. I can edit the layers comprising the GIF, of course, but usually cannot save the changes as a new animated GIF. Somehow it did work (sort of) the first time I tried. I had 79 layers, edited 7 as a test, and saved as a new GIF. I could not adjust the timing; that was greyed out. The resulting GIF did animate, with my changes visible, though the animation was choppy.

I suspect that I did not notice and try to select the Animate checkbox, because every time I attempted to do that subsequently, I got the “Save for Web can not animate the document because it is too big. To save this image as an animated gif, reduce the image size of the number of layers” message. I have searched this forum and the Web and have found no solution to that issue. In my experiments, I often saved the GIF anyway, without Animate checked. Sometimes, the resulting GIF was animated, while other times it was not (only a single layer was saved). I thought I would ask here before giving up and finding something else to experiment with. Anyone?