Hi @Liz_Kelley , welcome to the forum 
This is called ‘variable substitution’ and many are hoping that this will be natively built into Asana soon. Variables in comments as actions by Rules were recently announced but unfortunately there are no variables available for rules that create a new task (which is also a recent feature in the rules’ actions list).
Until then, I would recommend Flowsana that uses variable substitution so that you can create custom rules to do some pretty cool things.
Cc @Phil_Seeman