To modify the Atom's title bar text with your own pattern, you can use this plugin:
In Atom, go to Settings >> Install >> type custom-title in the search bar and install the package.
After you have installed custom-title successfully, go to Settings >> Packages >> click custom-title's Settings button and change the title pattern to whatever you want using its provided syntax. For example, I want the title bar display full file's path, I will use this following template:
<%= filePath %>