I want to add an option under Create New to create a file of particular type. For example I use Rnote to create notes,. They have .rnote extension.

Now I create a empty file (image, 3rd option from above) with extension as .rnote , but that file when opened in the application can't be written to, because it is not a proper .rnote file, it is empty file with that extension.

How do I quickly create a proper file for rnote or any application for example libreoffice?

I am on fedora 43, kde plasma.