Have you heard of Gabriela Pereira’s DIY MFA? She goes through a pyramidal revision process. It starts with big things (plot, structure, etc.), then moves on to characterizations, and things like that. The last step is grammar, spelling, and line editing.
Here’s the DIY MFA site: https://diymfa.com/
I tried this approach with the last book I wrote. It wasn’t for me, but it might help you get a glimpse into how someone else has approached the editing process.
With the book I’m writing now, I’ve been trying something closer to how I write and edit my fanfiction work. I have big events in mind, but I outline, draft, and edit one chapter (sometimes two) at a time. It keeps me focused and makes me think logically about plot and characters so I don’t have to go back and wonder if my characters are out of character at any given moment. Basically, it checks off the characterization element of editing for me.
Working in chunks like this also keeps me focused on moving the plot along. Since I have the next big plot point in mind, every chapter has to take me a step or two closer to that goal, and since I already have at least three or four of the big moments (inciting incident, midpoint, climax, etc.) in mind, the structure cooperates decently (though, it does need tweaking at times).
That leaves line editing, etc. I go through every chapter after I’ve written it and make sure I’m happy with every word on every page. It takes time, but it means I can split up the tedium and do it in sections rather than trying to line edit a whole manuscript, which, for me, wasn’t such a great thing.
Jerry Jenkins has a great list for self-editing: https://jerryjenkins.com/self-editing/
Anyway. Hope that helped at least a little.