Currently, you can set the internal status to “Away” for another team member (e.g., if they are on sick leave and cannot do so themselves).

However, at the moment I cannot enable the automatic out-of-office message for such users (not even as an administrator).

My suggestion is to add an option that allows the admin to add such a message.

And even better: if we could define one or more standard out-of-office messages (in our case, in German and English) (i.e., different ones for vacation or sick leave) and have the system generate a dynamic response based on the start and end dates of the absence.