I see where you’re coming from, and I do agree - pixel-perfect progress GIFs are great to have.
I’m trying to think of a way this could work with the existing modification history but since each frame is more or less a snapshot of a totally different image I don’t see how PMNG would know how to put together the progress recording you’re after.
Like you suggest - I assume this would require a brand new feature that would simply record a composite state of your project every time you made a change.
But, would it record when you play back the anim to test it? What about changing the canvas size or altering the palette after it has already recorded frames with up to 256 colors?
The WIP recording could just show a continuous loop of your animation playing (at a preset frame delay?), the loop length increasing as you added frames. This would capture how the animation progressed over time but wouldn’t capture every little edit made to every frame (unless one loop elapsed per single edit which doesn’t seem preferable at all).
Could be an impressive feature. Would need a voluntary ‘start recording’ button I’d imagine.
Alternatively, there was a suggestion of giving PMNG multiple preview windows, kind of like what Photoshop has. With multiple preview windows, you could use one normally while working, and devote another one (set to continuously animate) for screen recording using a lossless codec.