Found this previous discussion from not too long ago:Can a task in one project show up in another?
Should fit, though I'm not a producteev user myself yet.
Bruno's answer was:
You can definitely display some tasks from different projects by using the filter "due today" at the top of your task list.You can also use the labels if you prefer to maintain a "manual" categorization of your tasks
Thanks for the quick reply!
I think that will work.