Required fields in checkout do not create the red bar
You can decide the fields that you want to show/hide on the Hosted Checkout Pages and Customer Portal, as well as if the fields should be mandatory or optional. If the field is set as Mandatory, the user cannot move to the next window without filling it and it will display a red bar indicating it is an obligation.
To configure your fields, go to Settings > Configure Chargebee > Checkout & Self-Serve Portal > Field Configurations.
Now, on the right-hand side of the field, you will find a toggle button to enable/disable the field on the Checkout/Self-serve portal and a pen icon to edit the field display settings.
By clicking on the pen icon or edit button, you will get a list of options to set the options to display the field as follows:
To set a field as Mandatory, select that option and click ‘Apply & ‘Publish’
Now you can use ‘Preview Checkout/Portal’ to preview the updated changes.
This is how it looks if a field is set as ‘Mandatory’ on the Checkout.
To know how to set a Custom field as Mandatory, refer to this article How to create a custom mandatory field?
Related articles and documentation
How to remove the “Ship to my billing address” option in Checkout?
How can I hide a particular address section (Shipping/Billing/Card) on the V3 checkout pages?
Pre-filling/Passing custom fields to hosted pages (via Plan URL)
How to remove/edit the sidebar content on the checkout page?