So, I'm updating my mod when I have time to kill, and when MCreator got the 1.15.2 compatibility I made a big update for my mod and added a dimension too. The problem here is that:
When entering the dimension, you will be around the same coor', logic, BUT it can be into a wall, in mid-air, etc... and the portal will never spawn at your position, it will randomly spawn in the dimension open space(I did a nether with a custom biome) that is the nearest to you, so to return to like your house(asuming you made the portal in your house, you need to recreate a portal where you spawn in the dimension(hope It's clear). And also, every time you get in the dimension it create other portals into it.
(I took 6 screenshots, so, opened paint.net and made one image out of the 6, tell me if the quality is good or not.)