To mark a terminal as 'no connection required' click the Add→Wire→ button.
As you move the mouse in the schematic you will see a red cursor.
Red 'no terminal' cursor
If you move the mouse over a terminal it will turn green.
Green 'terminal' cursor
Left-click to mark a terminal as 'no connection required'. A green diagonal cross will be added to the terminal to signify that no connection is required for that terminal.
terminal marked as 'no connection required'
Deleting 'no connection required' Markers