Mac mini (2012) with multiple monitors

[rich1812]

Hello, my Mac has 3 monitors. The center one is the main monitor and the two on the left and right are USB and HDMI connected monitor. I used to be able to drag the drives icons, folders and files to any of the monitors to keep my my things nicely organized. But the other day, I had a power outage, when the Mac reboot after the power returned, everything changed. I can no longer drag the disk icons and folder icons to the left or right monitor. Every time I drag them, the Mac automatically bounces them back to the center monitor. I use Mojave 1.4 (not the beta.) Is there some setting I don't know about? Thanks.

 

[leventozler]

https://support.apple.com/en-us/HT209101

 

[rich1812]

Thanks for the reply. I did not realize the term is stack, silly me.
But can you tell me why after the power outage reboot, the use stacks would change to checked?