FreeCommander

Activating the main menu item "View → Quick view panel" or the shortcut "Ctrl+Q" switches the quick view panel on/off. In the quick view panel the item highlighted in the active panel is shown separately:

The quick view panel stays open (even, if other items are highlighted in the active panel) as long as it is not closed by activating the main menu item "View → Quick view panel" or the shortcut "Ctrl+Q".

Where and how the items are shown (according to their type) can be defined under the main menu item "Tools → Settings → View → Viewer".