I recently tried to make jelly-topped cookies (specific recipe was from home, but here's an example recipe) using an assortment of flavors, including maple syrup, homemade sumac syrup, homemade elderflower syrup, vanilla flavoring, and a pandan flavoring that I bought at my local Asian market. I thought I could just make a dent in the cookies and fill them directly with the flavorings; I was wrong. I sort of expected the liquids to cook off (which happened), but I thought they would at least leave flavor residues behind (that did not happen).
My goal is to be able to make small amounts of a bunch of different flavors and then use them to bake a single batch of cookies with a diversity of different jelly toppings. I already make homemade syrups for pancakes and marinades and the like; I'm not going to go through all the effort of making and storing dozens of different types of jellies too, not for just the occasional baking day.
So what is it about jelly that makes the flavors last better through the baking process? What would I have to do to a liquid flavoring to make it last through the baking process? If I made a paste out of flour and liquid flavoring, would that hold the flavor? Is gelatin important/useful in order to retain moisture? Any and all help appreciated!