Hi,

The missing red asterisk for mandatory fields in your Odoo Online Studio modules is likely due to Studio form view overrides or widget issues, given you've correctly set required=True at the model level. Since custom modules are not an option in Odoo Online, start by carefully reviewing and simplifying your Studio form view customizations. Try different field widgets and, as a less ideal fallback, manually add a red asterisk using a static text element styled with CSS if possible.

Contacting Odoo Support is highly recommended to report the issue and seek guidance, as it might be a bug or have a known workaround. Consider submitting a feature request for more consistent red asterisk display in Odoo Studio. Remember to thoroughly test any changes in a staging environment.

Reference:-

* https://www.youtube.com/watch?v=laF9XUPaCc4

* https://www.youtube.com/watch?v=5jrwei9tM8s

* https://www.cybrosys.com/blog/how-to-customize-views-reports-in-odoo-18-studio#:~:text=In%20Odoo%2018%2C%20the%20Studio,Views%2C%20and%20Analytical%20Reporting%20Views.

Hope it helps