I have a collection called "blurbs", which contains a field called "category" (which references a collection called "categories"). I want to have a dynamic page with all the blurbs of a particular category. But, when I try to set up a filter such as by creating a dynamic URL, the category values are not available to choose (the "value" downarrow is grayed out) so a filter can not be set up. That same thing happens if I try to set up such a filter for a repeater on a static page. I see that the documentation says "This feature is not available to all users" so is that why it's not working?