making a sub-document into a main folder

just started my Scrivener experience (relatively new to Mac too!). How does one reclassify a sub-folder which is indented under a main folder into a main folder (move it left in Binder)?

Drag and Drop, if you prefer the mouse. The four arrow keys can be used in conjunction with Ctrl-Cmd modifiers to move an item around spatially, if you prefer the keyboard.