I have a Macbook Pro connected to two external displays via a docking station. With the lid open, it will use all three, with the primary set to one of the external displays, let's say display 1. If I close the lid, the internal display shuts off, which is great. However display 2 now becomes primary, and all the windows on display 2 move to display 1 and vice versa. I open the lid, and it switches back. Not that big a deal just a mild annoyance, but I have not found any information about how to make it stop.
Catalina 10.15.6, MacBook Pro 15 inch 2018
Radeon Pro 560X 4GB
Intel UHD Graphics 630 1536 MB