Journal or Diary App thats both secure and customizable

Looking for a private journal app that is customizable in font size and style and similar functions to Libra writer. Why you ask? *I am a Tinkerer, and a Philosopher of sorts, and am looking for that **"just right"** packaged app that meets these primary specs:* Encrypted, Secure, in Ubuntu or Debian, and similarly customizable to Libra Writer as far as fonts and text size and shapes goes, and also contains a simplistic toolbar for object creation with various geometric shapes and sized objects for point & click ease. Also a simple header or title block creator to start each new thought or idea would be fantastic! Also, I am somewhat new to Linux & Unix, and any terminal command line syntax to simplify installation or functionality and ways to encrypt is greatly appreciated! Thank you kindly as well, Rudy