For example I have a Project Variable 'Previous Sprint' which is set to a sprint card. I want to display a property of this card ('Percentage Done'). Something like the following would be nice (using say "number" or "card"?) but unfortunately it doesn't work. Is there a way to do this without defining yet another project variable which is a property of the card I want?
value query: SELECT 'Percentage Done'%
WHERE Type = 'Sprint' AND number = (Previous Sprint)