The Menus > Expand submenu

The Expand submenu allows you to expand the selected directory tree. You can choose to expand all directories, expand directories to a certain level or expand only directories larger than a minimum size.
You can find it as a submenu of the Branch menu and in the directory tree context menu.

Full Expand	Expands the selected folder and recursively all its sub-folders
To Level x	Selecting this menu item will show the first x levels of the current folder
Expand Folder over x MB	This menu item allows you to expand only those folders in the tree which are larger than a certain size.
Set Minimum Size	Allows you to specify the folder size for the above operation.