I think you might appreciate https://www.jj-vcs.dev, which makes it a lot easier to split and recombine changes. I often use it for checkpoints, although you wouldn't see that from looking at what I push :).

One nifty feature is that commits don't need messages, and also it'll refuse (by default) to push commits with no message. So your checkpoint commits are really easy to create, and even easier to avoid pushing by mistake.