“additions” are one of the three parent-child relationships we support for the inventory in Cumulocity with the other being parent-child device and parent-child asset. The latter two will impact how the inventory objects are shown in Cockpit and device management (e.g. on the child device tab of a device in Device Management).
“additions” are a generic parent-child relationship that will not have such an impact. It can be used e.g. for access control if a user does not have full inventory access but only to specific groups.
Cumulocity provides three different parent-child relation types: child devices, child assets, and child additions. Functionally they are all very similar. They allow adding objects into the hierarchy for various purposes (e.g. access, permissions, sorting, etc)
Child devices are usually used to connect a device to children that are connected to the platform via their parent device
Child assets are used for groups and devices in groups
Child additions don’t have a specific purpose. They are typically used whenever the use case doesn’t fit child devices or child assets. One example here is entries in the software repository where we have Software objects as parent additions and their concrete versions as child additions.