Help → Lepton EDA Reference Manual (H M) will open the manual you’re reading just now in your HTML browser.
Help → gEDA Wiki Documentation (H W) will open the documentation page of the legacy gEDA wiki in your HTML browser. It may still be helpful in some cases.
Help → Find Component Documentation (H C or H O) tries hard to find any documentation for the first component amongst selected objects. If no component is selected, the action is unavailable.
Help → Hotkeys... (H H) may be used to look up for some action you do not know shortcut for. It displays a dialog with all action menu names and their corresponding hotkeys.
Help → About (H A) opens the standard GTK
About dialog with some useful information on lepton-schematic.