As a DM, I've been using a Mummy, and as a result, the character of one of my players has had their hit point maximum reduced a lot. In my head, it was clear that the character would go to the nearest town and ask the priest to heal them; the priest can cast remove curse to halt the bleeding and greater restoration to end the effect reducing their hit point maximum. However, they only removed the curse (by spell swapping at a level up) and went on.
So I might throw another way to get their hit point maximum on the road, but what? Besides greater restoration (and wish), what are the other ways of ending a reduction to someone's hit point maximum, especially at level 4-5?