I'm working on a gallery with a selection feature - it's super simple in concept, a gallery of images that will change the image state with a checkmark and border treatment when selected. The problem is, I've got a dozen images in the gallery, if I were to make every single possible iteration of the page it would be like 144 pages.
Is there a way in XD to isolate the state change to a single element on the page without having to make a second page showing the changed element state?
What is your goal here with this project? If you are trying to create a fully functional web page/app, that is NOT what XD is for. As you pointed out the combinations quickly grow. Sadly, what you want are more complex component-like capabilities. Currently, those don't exist. Depending on what you are trying to do, either just so a sub-set to demonstrate the basic look you want to show, or work out the development and have a functioning version. This is where having the coding ability in Adobe Animate (aka Flash) would make this so easy.