How to add new yaml headers in Rmarkdown (pagedown)?

Question

I've seen these header in the thesis template's yaml header that comes with pagedown package Can I add some other categories like: period, surname, deadline, any? Are these predefined with the thesis template? Can I create my own template with some particular yaml headers?

• author
• degree
• institute
• faculty

etc

title: A paged html thesis template for R Markdown users
subtitle: A {pagedown} template.
author: 
  - name: William Brent Thorne
    edu: BSc
degree: Master of Documentation
institute: Typeset University
faculty: Reproducibility and FOSS
department: Templates
location: St. Catharines, ON 
date:
  - year: 2019
    month: August
sign_page: true
dedication: A dedication line or two goes here.
abstract: This is the abstract.
preface: A preface to the thesis.
acknowledge: Put the ackknowledgements here.
committee:
  - name: Jane Doe III
    prefix: Dr
    position: Chair of Department
  - name: John Smith
    prefix: Dr
    position: Faculty Advisor
lof: true
lot: true
toc-title: Contents
output:
  pagedown::thesis_paged: 
    toc: true
    number_sections: yes
    pandoc_args: --mathjax
    self_contained: no
bibliography: packages.bib
link-citations: yes
# uncomment this line to produce HTML and PDF in RStudio:
knit: pagedown::chrome_print
---