Thank you for your question. It sounds like you are looking for an allow list only option. Unfortunately, at this time we don't have that as an option. We are able to block entire domains, like Facebook to use your example, but cannot then allow specific pages within Facebook simultaneously. I know that there is software out there than can offer an allow list only option. I just don't know which filters specifically offer that as a feature.
I will say that if you use iOS devices that have up to date operating systems then the devices themselves would offer an allow list only browsing option within the settings of the phone or tablet.
Thank you and I am sorry for not having a more ideal solution for you at this time.