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.)
Issue comments
Am gonna send you the workshop of my mod, Portal is made of "Blue Mountain Dirt" and there is a "Blue Cave Igniter" and then you will see. https://www.mediafire.com/file/a9moht5vsxrdsiq/undersource.zip/file
I can confirm there are problems with portals I am working on but was not able to find a clear resolution yet.