they used to allow the substitution of 2-3 snacks for a counter service credit, especially at resort counter service...however, this year many people have reported being turned town on this.
We were at POFQ twice this year, and both times the people at the counter service were telling customers the only way they could get "snack" items was to order a continental breakfast: specifically they could choose one pastry item, one fruit, and one beverage as a contintental breakfast and use a counter service credit for this. They had a printed card that showed the exact combinations allowed (for example,you could not get biscuits & gravy as one of the components.)
Something you could do, depending on what time you're leaving...maybe get a cold lunch to take on your trip home (prepackaged sandwich, chips & bottled drink.) That would use up your CS credits.