Tub P Trap Height

Need to move to new location, about 36 inches. under slab

If I remove old P, run horizontal 2 inch for 36 " to new spot, I will need slope on that 36" run which means new Ptrap will be about 1 inch higher than old one.

Is that a problem, or is there a better method? I don't think I want to run that 36 inch without any slope, right?

pipe

If I remove old P, run horizontal 2 inch for 36 " to new spot, I will need slope on that 36" run which means new Ptrap will be about 1 inch higher than old one.

Correct.

Is that a problem, or is there a better method?

No problem unless it creates one in your situation. And without seeing it we cannot tell if there is a bette way.

I don't think I want to run that 36 inch without any slope, right

Definitely not.