Right now, as far as I can tell, there is no way to move/reorder multiple css rules in the built-in editor panel.
You can drag/reorder individual rules with the triangular drag handles, and you can CTRL click to select multiple rules to move them to different files/duplicate/disable/delete, but there is no way to combine these efforts and move/reorder the selected group up/down in the same file together.
It would be nice if this could be implemented. I would also propose adding keyboard shortcuts for moving the selected items.
You can multi-select classes, but you cannot move the multi-selected rules up/down within the Bootstrap Studio Style editor hierarchy
But, you can configure an external editor that has this ability, and use it as a work-around if this feature is never added to the BSS editor (which it likely won’t be. I’m pretty sure it was because of requests like this that the devs decided to add the ability to use external editors - because the internal CSS editor is sort of limited, but others (like notepad++) could do this easily with a copy/paste. This way they can focus on improving the BSS program itself, and let more powerful external editors like Notepad++, Atom, Visual Studio, etc, do the heavy lifting.