How can I move spaces between external monitors in Mavericks?

Solution 1:

You can only move spaces which are non-active.

For example, lets say you have spaces 1 and 2. If space 1 is active, you can not move it. You first have to select space 2 then you can move space 1 to a different monitor.

Solution 2:

TotalSpaces allows you to assign spaces and their contents to specific monitors.

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