Main Window - Options | Which Files | Child Folders                    Ctrl+Shift+N

Thumbnail View Popup Menu - Which Files | Child Folders

Folder Popup Menu - Show Child Folders

Volume Popup Menu - Show Child Folders

 

 

This option toggles displaying in the thumbnail view all files from the current folder and its sub-folders. Whenever you change folders, this option is turned off (to avoid the extremely long delays when changing to a folder with many sub-folders). To always show child folders without having to select this option, check the Always show child folders option on the Options | Preferences - Thumbnail Views settings tab.