You can move blocks from one building to another using the Transfer blocks command accessed from the Edit menu when the site contains more than 1 building. This menu option opens the Transfer blocks dialog below. Select the building containing the blocks to be copied and the building to receive the blocks and Press OK.
Note: You should check before starting the block transfer that none of the source blocks overlap with blocks in the destination building. Even a small overlap will cause the whole process to fail.
A Transfer block operation cannot be undone and it clears any existing undo/redo information.