Global CSS & JS for Jira makes it possible to add custom CSS and Javascript to Jira using custom editors.
Customizing Jira
Go to the "apps section" of your Jira instance.
- Navigate to "Get Started" under "Global CSS & JS"

- Choose 'Add sample code' to add some pre-made CSS and Javascript examples or 'Add my own code' to customize Jira with your own custom code.
