Task Flow question - Navigable Nodes LOV doesn't list needed Task Flow Unit

How do I add the needed Task Flow value for Navigable Nodes LOV - is it possible at all. I was trying to add a new navigation option for one of the HR TASKFLOWS but this option is not available in the navigable Nodes LOV.  From the manual - it seems - to appear in this LOV it should have In and OUt globals. How do I proceed from here in order to add a new row for the Navigation Options.

Thanks.