I have a 2017 27" iMac that generally has one external display, connected to the DisplayPort port of a OWC Thunderbolt 3 Dock. This display is always connected to my mac.

Occasionally I will also connect a thunderbolt 3 external touch display for work. Up until today, that display was always considered display #3 and wouldn't affect the icon or window placement of either of my other two displays.

However, today I booted up my system with the external thunderbolt 3 display connected, and now macOS considers it to be display #2 as long as it's connected. All of my carefully arranged desktop icons that used to be on my DisplayPort external display now get kicked over to this thunderbolt 3 display. If I disconnect it, the DisplayPort display becomes display #2 again and the icons reset. It's very annoying!

I haven't found anything I can do to reset this behavior. How can I get my displays back to working the way they were before, with the thunderbolt 3 display always being display #3?

  • what does it do if you restart without it been connected. – Ruskes Nov 13 '18 at 21:26
  • @Buscar웃 It will still take over as display 2 even if I disconnect it, reboot, and then reconnect after my DisplayPort display has been recognized as display 2. – GuyGizmo Nov 13 '18 at 21:34
  • can you look in to /System/Library/Displays/Contents/version.plist and tell me what is says there, is your display showing,,,and in the /System/Library/Displays/Contents/Info.plist – Ruskes Nov 13 '18 at 21:53
  • @Buscar웃 I'm not sure what information you're asking for. Do you want me to copy the contents of those files into a pastebin so that I can send them to you? They don't mention my display of course, and they just show the typical information you would see in those files for macOS 10.13.6 (which is the macOS version I'm running) – GuyGizmo Nov 13 '18 at 22:58

I've found one solution to this: reseting my mac's NVRAM. This seems to reset the order of my monitors to how it was before. However, if I leave my Thunderbolt 3 display connected while booting my mac, the problem will come back again.

I'll wait a while before marking my own answer as the accepted solution to this question since a) it's not a particularly good solution, and b) I'd like to give other people a chance to post a better one.

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