Make sure you’ve read the general notes about all the nodes: Reference - nodes

Objects add

This node allows you to merge several sources (any number) of SceneCity objects into a single source. That way you simplify the graph by having fewer nodes, for example less objects instancer nodes, because this type of node takes a single source of SceneCity objects. It is also less clicking when the nodes you “eliminate” need you to click on them to do their job.

The objects added together are not modified in any way.