It’s fairly simple, just create a file in the ~/Templates folder, it’ll show up in the right click menu
1touch ${HOME}/Templates/Empty\ Document
The only caveat is that you have to rename the file after it’s created.
I used the name 1_Markdown.md for my file.
.md extension because 90% of the files i create in Nautlius with the right click menu are Markdown files. I made other .sh, .js, .scss templates too..1_ at the beginning means that it shows up at the top of the list view in the folder when it is set to sort A-Z