Stacked diffs have been a pain for me as well, but recently I found a tool that makes it super easy to implement stacked diffs on top of GitHub! I started using it a month ago and it makes complex code changes so much easier to split up into manageable chunks.

It's called ghstack (https://github.com/ezyang/ghstack)

If you want to learn more you can email me at [email protected]. Also happy to help you get it up and running - just put some time on my calendar at https://calendly.com/ericyu3/15min