Make a CalDAV as default calendar

Hi, Using EmClient for a gmail and an infomaniak (Etik as domain name) account. Is it possible to make my Etik calendar, not my gmail calendar, as the default calendar? When I click on “define by default” in my infomaniak account, I receive an error message.
Thank you in advance

I think you want to go into the CalDAV/CardDAV tab and then under Default Folders, select the calendar that you want to be the default for Calendar.

That is what I was indeed trying. But doing so, I get this error message

Your screenshot shows the General tab. Can you take a screenshot of what you see when you click on the CalDAV/CardDAV tab? I am curious to see what is Calendar folder setting is under Default Folders.

Voilà…