Open two Finder windows, side by side.
In one window open the source folder with the folder you want to move.
In the other window
In the other window open the target folder, where the folder you want to move will go to.
Now drag the folder you want to move from one window (source) into the other window (target).
If source and target folder reside on different volumes/partitions of the same HDD or even different HDDs, the folder will be copied, thus leaving the original folder where it is, even after the folder has arrived in the target folder. You now can delete the source folder.
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