Yes, it is possible to add custom CSS classes and IDs in HubSpot's COS templates; however, at this time, you can only add IDs to module groups.
- In your Marketing Basic, Free, or Professional account, navigate to Content > Design Manager.
To create a custom CSS class:
- Locate the module where you'll apply the custom class or ID. Click the gear dropdown menu to toggle the options. Select the Edit CSS option.
- If you would like to add more than one custom class to any module, simply add the multiple classes in the Custom CSS Class (advanced) box, separated by a space.
To create a custom ID:
- Locate the module group where you'll apply the custom ID. Click the gear dropdown menu to toggle the options > Select the Edit CSS Declarations option.
Once you've configured the custom class/ID names on your template, click the Publish Changes option on the template to push the changes live.