atom-switch-extension
A package that allows you to quickly switch between files with different file extensions in the same directory.
Switch extension package
A package that allows you to quickly switch between files with different file extensions in the same directory.
Screenshot
Configuration
Default file extensions: ['.js', '.html', '.css']
Default keyboard shortcut: Alt + O
Usage
Let's say the you set up the extensions to be .js, .html and .css.
If you then have a .js file open and execute the command (default shortcut is Alt + o) it will open the .html file in the same directory if it exists, otherwise it will try to open the .css file.