I'm sure there would be things like replacing the ball further in front of your marker, taking your stance in a way that gets some branches or grass out of the way of your swing, thing like that where you're not deliberately cheating but not thinking about what you're doing critically.
I played with a guy one day and he consistently marked his ball by sliding his marker underneath it as he lifted the ball. Then he would 'replace' the ball two inches in front. I asked him "Do you really think two inches closer is going to help you each time?" He was most indignant that I'd picked him up on it, obviously thinking that no-one would notice. He stopped doing it, but his putting didn't improve.
As for moving branches out of the way, you can fairly take your stance, even backing in to position. But what is fair? We all try and alleviate problems where possible.