Change default YAML of Rmarkdown file - r

Question

I want to change the default template of the Rmarkdown document. I edited the file named document.Rmd in the templates in the RStudio application folder so that the YAML is:
---
title: 'document'
output:
html_document:
self_contained: true
toc: true
toc_float: true
bookdown::pdf_document2:
extra_dependencies: ["float"]
toc: true
---
However, when I open a new Rmarkdown document from RStudio, I get a prompt that asks what type of Rmarkdown document I want. I choose HTML, click OK, and then I get the file opened with these two YAMLs!
---
title: "Untitled"
output: html_document
---
---
title: 'document'
output:
html_document:
self_contained: true
toc: true
toc_float: true
bookdown::pdf_document2:
extra_dependencies: ["float"]
toc: true
---
I do not want to go through the hustle of creating a package or a template. This simple solution should work, I think.
My question: Does anybody know how to work around this? Thank you in advance!

Answer 1

After reading your question, I found this source, which indicated that you could add a template. I also read that document.RMD does not include the YAML. That's why you are getting a double-YAML.
Since I had never added a template for R Markdown, I went through the steps to see how it all came together. That led me to create a repository on Github, and well, here we are. Essentially, I made a Github repository that you can install with the exact template you wanted.
You can also look at the code, as well. Since it was created just to answer this question, if you wanted it to be different, you can change it, as well.
You'll find the repository here: fraupflaume/customYAML
If you want to install it:
devtools::install_github("fraupflaume/customYAML")
To use it, you don't have to call the library (there's no R code). Start an R Markdown script, select "From Template," then choose "Custom YAML."