I find I work most effectively when I do the opposite of multi-tasking.
I think of it as batch processing, a term I probably picked up programming PASCAL in high school.
Essentially, I’m waiting to do a repeated task until I can do it a bunch of times in a row. For example, in the last 48 hours I did the same multi-step task fifteen times. (It was complex, involving two types of notation software, Canva, my website, and an online publisher.) The fact that I did it fifteen times in a row meant that after I learned my process with the first few, I was able to execute the bulk of them quickly and efficiently. Next time I have to do this, it’ll be a lot slower – at least at first.
Sometimes this means waiting a little longer to finish a project, because you need to get a batch ready. But in the end it’s worth it because of the gained efficiency.