It is easier coding-wise to have it only trigger the first item in the queue but when I play Evolve I almost always have it set to do anything in the queue and I use the queue to build houses and stuff, rather than clicking it whenever it is buildable. To encourage this behavior, rather than using the massive dropdowns have it so you can use a hotkey to click and add things to the queue.
Likely you don’t have the prerequisit policies to unlock them or the policies you have exculde them from showing. Take Monarchy for example. If you take liberty, which locks out tradition, you can never get the prerequisites for Monarchy and thus it will never show up.