Im trying to make a link a door from my private island I made to bruma and every time I change the cell it automatically changes to Abbandoned mine its very annoying and I cant uncheck the persistent reference icon

Dont know about the Abandned Mine part, but doors, once connected, must remain persistent, so the CS disables the checkbox.

The thing is it wont uncheck it has that greyish color that wont let me uncheck it

anyone going to help I have spent a long time doing this and I dont want it to go to waste

You don't want to uncheck the Persistent box anyway. Teleport doors must be persistent. If you could uncheck that box, your door wouldn't work anymore.

As for the Abandoned Mine issue - when you go to the Teleport tab in the door's reference window, in the top-left there is a checkbox that says "Teleport" next to it. That box has to be checked for your door to go somewhere else. The next dropdown is where you choose what cell the door will teleport to - it says "AbandonedMine" by default because that is, alphabetically, the first cell in the drop-down list. Click the drop-down and scroll through the cells until you find the one you want to teleport to. The next drop down lists the available doors in that cell, and from here you can choose which particular door you'd like your door to go to. Any doors that are already linked to another door won't be in the list, thus you have to be sure you place both doors before you try to link them together. Hope this helps.

the thing is when i change what cell it is then i click ok then i open my mages guild teleporter again then its abbandoned mine again it wont change and once I get both doors down to where i want them they dont have that linking thing

You have to click "View Linked Door" - this will open the new cell in the render window and place a teleport marker at the door you want, which you can then adjust as needed. Once you've got that done, repeat the process with the second door.

I've got a related question: If you have a door that's already linked to another door, can you move the first to another place in the same cell without causing issues? I've already tried it and it works, but someone told me that the door's coordinates are what matter. I tried moving the door without moving the marker; I can teleport to the new location, but when I come back through the door to the first cell, I end up at the door's original location, which is floating in the void. I just wanted to check with some folks who know more about this than I do.

There are two artifacts involved at each end. One is a mesh that represents the door visually, and the other is the door marker, that represents the position for the player movement. Either of those can be moved independently, and you usually have to re-position the door marker so that you face in the right direction, and aren't embedded in the woodwork when you teleport. There is actually no need to have the door mesh inside the accessible cell, and some of the vanilla game's interiors have the door mesh behind the wall. It's only needed because it's a standard part of the form with all the settings for the teleport process - which includes the door marker's details. Just think of positioning the door mesh as the visual aspect, and the door marker as the movement part, and it should all make sense. If you don't want to see the door, move it out of sight. Place the door marker where you want it all to happen (including hitting F to drop it to the floor.)