Hi,
i played around with API function /devicegroups

I tried PUT and DELETE /devicegroups/{path}/customAttributes/{customAttributeId}

Problem is that only free or new devices are affected, devices with edited Values will not get touched.

Swagger Page on DELETE:
Clears a custom attribute value for a single device group identified by its reference ID (recommended) or path. Requires the caller be granted the "Edit Custom Attribute Values" permission for the specified device group.

Is there a way to get this work on all devices like the documentation says.

Thanks for some infos about that