In Safari, click on the Bookmarks menu, then Edit Bookmarks.
Click Add Folder (bottom left corner)
A new folder will be created. Type in the name that you want.
Drag your new folder anywhere you like.
If you want it in Favorites, drag the folder to Favorites, to the position that you like.
If you want to add that folder to another, previously created folder, then just drag your new folder to that older folder.
If you want to drag THAT folder into another folder, then create a new folder that you then drag all the other folders at once, you can do that, too! (Gets a little confusing for me, but that's just me

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