The Knights Templar organization is actually a part of Freemasonry, specifically, the York Rite, as what is called an Appendant Body.
Please see more information at the Freemasonry Project.
Specifically, we are not creating categories for these Appendant Bodies, as there would not be enough profiles yet to warrant its own category.
What we recommend is that you use the [[Category: Freemasonry]] category on the profile, and then write a description in the body of the Biography about his Masonic affiliations, such as the Knights Templar.
Please let me know if you need any help.