What is the real issue? Why do you need nvmeXn1 to be "static"? Please make sure there is no XY problem here. [Edit] the question if there is. E.g. if you want to know a way to mount a partition reliably then ask exactly about this. We have
/dev/disk/by-uuid and such. Or is the problem with booting like the title (but not the body) of the question suggests?