Short answer… Nope 
In fact I had just posted an idea on SAP’s page this morning for this very issue:
BI4 - Allow Prompts to be grouped in SETS for ‘required/optional’ ability
And it seems there is an identical one from almost 6 months ago at:
Improve optional prompts
Perhaps if enough people vote those up, SAP will take notice and implement it 
Ohh and Welcome to BOB! 
Here’s another thread with all sorts of ideas you might find interesting:
SAP Idea Thread
JPetlev (BOB member since 2006-11-01)