[Christian]

I see the issue with that. What comes to mind is

- a more regular review process. If you review all tasks once per week like many do (me for example) then you will be reminded to ask person X at least once per week.

- configure your perspectives so that @waiting tasks are shown. Assign a starting date in the future (maybe a week) to such tasks that depend on third party actions. That way they will at first be hidden but magically appear a week later, reminding you to ask bob about ABC's status.