You can place custom JavaScripts under Customize > Custom JavaScripts and this feature is controlled by Flexia Core plugin. Make sure you have Flexia Core installed.

Also make sure your WordPress version is greater than 4.9. Since we are using integrated CodeMirror editor which is available from WordPress 4.9, it won’t show the option if you are using older WordPress on your site.

Installing Flexia Core:

Way #1

• Go to Appearance > Install Plugins  page from WordPress Dashboard
• You will see the option to install recommended plugins
• Select “Flexia Core” and install.

Way #2

• Go to Plugins page from WordPress Dashboard
• Click on “Add New Plugin”
• Search “Flexia Core” and install.