The new ServicePortal will present all active grant numbers to customers within Step 3 of the Create Service Request process, and Submit a Sample. This represents a significant improvement over the previous portal. With that said, we are looking at ways to make this even more seamless by systematically selecting the most appropriate entitlement on SR and Sample Submission creation. I agree with you that this would be the most ideal situation.
That field does support type ahead, so if you know the first few digits of the grant number, just type it in. This way you won't have to click on select from list.
Thank you for the feedback,