Not sure I have the answer - first all, I only have 1 HC, secondly, I just did my first link/MU myself. Learning as I go and reading this.
I was shocked at first when I tried the MU having the 2 uncoupled ... didn't work being uncoupled, once coupled it worked.

Also surprised the MU is remembered after on/off ... glad to see this. Now I have to learn about unlinking/clearing list.
I think on one of K-packs videos he talked about clearing thing.

My guess to your situation is the HC initially used to set up the link remembers the MU'd pair? Not the modules. I c/b wrong - but my assumption.

You are right - it is nice feature, and was happy it works, can't wait to do a 4 unit lashup.

I'm following this ..

The handheld controller keeps an internal list of modules it has controlled / is controlling. Normally after an amount of time (2 minutes I think) of non activity of a module it's automatically dropped from the active loco's list. Reportedly this sometimes didn't happen and if I recall correctly one of the side affects was you couldn't select the module again if it had been part of an MU. I seem to remember one of the reasons this could happen is not waiting the 2 minutes after finishing running and turning off the handheld controller.

The button simply clears this internal list.

- Tim

I linked my first pair of diesels about a month ago. Boy is that sweet!
I then removed one of the diesels back to the workbench to install forward and rear (LED) lights that were originally overlooked.
I put that unit back on the layout and married it up to its partner. I then randomly picked up one of my four HC-2b's. When I selected either of the two loco's, the HC-2b did NOT indicate either was linked. I thought that maybe somehow they became "unlinked" when I removed the one to my workbench? I attempted to link them again and it said that it couldn't because it was already linked!? Same happened for the other loco in the pair. The HC-2b did not show the "Unlink" button for either loco.
I then searched this forum and found a "Can't unlink" discussion from July '24. It discussed needing to try using the "clear active locos list" button, and try linking again. I reflected on this and wondered if my issue had something to do with the fact that I have four (-4-) HC-2b's. I started going through each of my HC's and the first two showed the same thing - that the two loco's were not linked. When attempting to run either of the loco's from these first two HC's they operated independently and dragged the 2nd unit.
Then when I tried the 3rd HC, it showed that they were linked and they did operate as a linked pair.
It appears that the linked status of the two units does NOT translate across, and to, any other HC's. Is this true?
If true, then I will have to either A) unlink prior to shutting the HC down, or B) put a note on the HC that has linked locos.
Anybody have any further info on this issue?
What is everyone's exper

Sorry, There is no way to transfer to the physical handheld from the sim that I am aware of.

If you're using the HC Simulator Switcher, I can send you a storage file that has the original file on it.