Why are some desktops locked during a dual monitor set up?
The space that you want to move to another monitor cannot be active.
For instance if you are currently on &quot;Desktop 1&quot; you can move any space to any monitor except for &quot;Desktop 1.&quot;  If you want to move &quot;Desktop 1&quot;, you need to switch to a different space and then move it to the monitor you want.