:expand-directory will show its children, :collapse-directory will hide them.

If a child is selected, it'll always be rendered in the list as a child of its parent, however, if the parent is collaposed, only the selected child will show.

Expand :next-folder and :prev-folder with an argument (-x) to support expanding folders with children while scrolling through the list.

Expand account defaults to support nested folders, delimited with /. IMAP servers which use a different delimiter will be corrected by the worker. Collapsed directories will always show children which are explicitly requested via the defaults config option.