Marking is usually an important step when it comes to A/B/O as it showcases how the relationship evolves and the trust both parties have on each other, that being said, not all the A/B/O marks are actually permanent. A kind of temporary mark exists in some iterations of the made up lore, and they work just like normal marks but disappear with time, I think the main difference is that they aren't as deep.
It is an interesting thing indeed, because in most iterations permanent marks are visible and not only that but often times change the pheromones of both involved parties, taking after one another.
I feel like it also important to point out that depending on the material you read a permanent mark is not always enough to bond you to someone for life, in a lot of the more romanticized versions an alpha marks an omega and only if the omega is allowed to mark the alpha back they can be bonded for life. The unfortunate thing is that if one of the parties dies, the mark doesn't disappear, which disallows moving on. You have to think of the permanent mark and bonding as a kind of marriage certificate that is relevant even if death does us part.