Calendar, automatic subscription to "Contact birthdays" cannot be modified?

The disroot calendar seems to automatically subscribe to “Contact birthdays”.
Somehow, I cannot edit this subscription, such as the name or the color?
Is this by design?

Thanks

The Birthday calendar is generated automaticaly from the contact list. It is indeed not editable.
There is a feature request and discussion here so we’ll have to wait and see if it is picked up by anyone.