Options - Subfolder menu

Include not only folders but files in menu

By unchecking this, menu will have only folders.

Include items that have Hidden attribute in menu
Include items that have System attribute in menu

This allows to enumerate invisible items in the menu.

Show preview tooltip

Displays Preview window of mouse hovered or selected item.

Show only with Shift key down

Blue arrow window won't be visible without Shift key.

Display even if folder window is not active

Blue arrow window is displayed over folder icons in inactive window by mouse hover.

Expand group items to the root menu for .QTGroup file

Members of groups in a Group File are included in the root of the menu.
If unchecked, group names are at the root of the menu and members of groups are under theme.

Show menu for folders under the mouse cursor while dragging files and folders

Enable menu for compressed folder

Currently supports zip and cab.

Show ghost while menu is displayed.

When your mouse cursor points another folder while subfolder menu is displayed, shows gray arrow window.
You can click on it to show subfolder menu for the folder. This saves one click to set focus to the window and show blue arrow tip.
(But come to think of it, this doesn't need to be optional.)

In Libraries, sort items in each folder

Sorts items in each folder instead of sorting all items at once.
(This too.)

Use custom color settings

If you have set Custom colors and Compatible View, apply colors to subfolder menu items.

Enable for items in the Command Bar

Enable for items in the Command Bar (vertical) Show blue arrow window for Command Buttons that represent folders.

Sorting items by

Specify how items in the menu are sorted.

Menu opacity

Makes menu translucent.

Drag hover time before the menu is displayed

How long you have to wait before the menu is displayed for drop hovered folder.

Delay time before preview is displayed

You can set how long you have to wait before preview window is displayed for mouse hovered menu item.