this video show how to add create new custom file types not just text file
-steps to add menu entry to create new .docx file ... how to do so
1. Go to Templates folder in user home directory
2. create .desktop file
3. create .source folder and create empty file as Template source
we need to save the file as docx format ; using libreoffice to do this job
"untitled.desktop" file content:
##################
[Desktop Entry]
Name = untitled.docx
Type = Link
URL = .source/word.docx
Icon = libreoffice6.0-writer
##################