Not sure if anyone still needs it, but I found a workaround that works at least for me
There is an
app in a
Mac AppStore called
Amphetamine. It simply allows you to disable sleep when you close the lid. That prevents a display from going in and out... You can also set up trigger automation, lets say when you have more than one display connected automatically run the app. I'm also suggesting setting up a built-in display as a mirror to 1st external monitor, which allows for the mouse not to run away from you behind the screen border...