Splitting up a PR is a lot of work, especially if you want each commit to compile, but it would be great if you could categorize changes using 5–10 colors and then have checkboxes that you can toggle to hide code corresponding to a color.
What each color means would depend on the PR, but, for instance, yellow = refactoring, brown = test code, blue = drive-by fix, orange = more efficient data structure etc.
The colors and their meanings could be set by either the author or the reviewers. It would be similar to the file checkboxes that exist today, but in this case, it would be per concept, not per file.
How it started: "It would be great if you could categorize changes using 5–10 colors and then have checkboxes that you can toggle to hide code corresponding to a color."
How it's going: https://gitmoji.dev/
IMHO, the novelty wears out fast. Especially when your git history starts looking like a Messages thread.
It would be in the "Files changed" section on GitHub, not in the git history. If you don't want to see the context, you can turn it off.