This would probably be an addition to projects. Sometimes something falls outside of your control and you have to wait for something else to happen first. I should offer the ability to mark a task/project as waiting on something and:
If it's waiting until a known date and time, enter that and "pause" the next action / prompts for defining a project's next action until after that date and time pass
If it's waiting an indeterminate amount of time, keep it in a sort of review list (I'm considering this review view to have "waiting on" actions, deadline actions, and projects, likely separate from the next actions view) so a person can regularly keep track of them and follow up if needed.
This would probably be an addition to projects. Sometimes something falls outside of your control and you have to wait for something else to happen first. I should offer the ability to mark a task/project as waiting on something and: