Hello,
Thank you for posting in the Microsoft community forum.
According to your description, the desktop ICONS rearrange themselves when the external monitor is inserted or removed. May I know if your users choose to extend, copy or just display the second screen when adding monitors?
If it is a problem when expanding, the phenomenon may occur because the screen resolution changes when switching between different monitors. Go to "Settings" > "System" > "Display" and test the resolution and scaling Settings consistently.
In addition, outdated or incorrect graphics drivers can cause problems with display configuration. You can download and install the latest drivers through the manufacturer's website
I hope this helps.
Best regards
Jacen