Another power feature of Nirvana is the ability create check-lists (sometimes referred to as sub-tasks) inside your action notes. Use check-lists for things you need to remember as part of an action, entered as separate lines inside the notes field, each line beginning with a dash.
New Action: Call Mom
Don’t forgot to discuss…
– flight # and arrival time
– gifts for the grand kids
– where she’d like to go for dinner
Hit Save, and lines beginning with a dash will render as check-boxes.
That said, if you need multiple actions to get to “done” you should really create a proper project with actions inside — all-the-better to keep your contexts, energy levels and focus/states current and your GTD system clean, clear and under control.