Share calendars/events with 'busy only' via caldav and android




maybe some can give me a hint:
I'm syncing and sharing my android calenders through owncloud 9.1.4..
I just found out that it is now possible to setup events with the option 'show as busy', which is very useful for my use case. Unfortunately, although lightning/thunderbird shows this option on my pc, I cannot find any way to set this in android, since only 'private' and 'public' is available in my calendar apps (businesscalendar, default-calendar).
I'm using caldav for syncing.

Does anyone know how it would be possible to use this function via android?

Thanks and regards,