Is it possible to reorder spaces in Lion?
Currently, it doesn't seem possible to just drag and drop the desktops to change their order.
Is there any other way of doing it then?
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Per my answer on a related question (Why do full-screen applications change their order in Mission Control?), there are only two order states with Mission Control. Order generated as Desktop/Full Screen spaces are created, or the default; "Automatically rearranged based on recent use" which I admit that I have no entirely narrowed down exactly when it changes them.
As of this writing, in OS X Lion 10.7.1, there is no way to explicitly order spaces except to remove and re-add them in an order you would prefer, after unchecking the checkbox listed in the screenshot above.
Well i guess you're asking this because mission control 'automatically' changed the order you set up for your spaces.
You can't move them right in Mission Control but what you can do is disable that 'magic automatic ordering' in System Preferences => Mission Control => Disable Checkbox "Automatically rearrange spaces based on most recent use" Then you can order them again using the Spaces Preference Panel.