It is all right because the arrows aren't doing the computations.
How are arrows not cheating?

yeah but they help visualizing. If i set up a board before me while playing with which i would start to analyze the position you would have a problem with that, right?

Imagine i would use a plugin to actually move pieces on the board for my calculations, everyone would accouse me of cheating. But arrows are okay?
Yes

Imagine i would use a plugin to actually move pieces on the board for my calculations, everyone would accouse me of cheating. But arrows are okay?
Yes
now you are supposed to state your reason

Does arrows helps in your calculations? Yes it does, specially in end games where the pawns are in a running
Why is it allowed? Because of educational purposes, many teachers uses it for Youtube/Stream so viewers can go through their thoughts, even if we admit that it’s cheating because of the advantage still everyone can use it.
When did arrows become a thing in online chess?
I personally never use arrows because i like to play vanilla, but why is it acceptable in the first place?
You can literally mark where the pieces go visually on the board by using arrows. How is this not cheating? Imagine i would use a plugin to actually move pieces on the board for my calculations, everyone would accouse me of cheating. But arrows are okay?