Also are there any examples for how to use it?

Scene Nodes and Mesh/Body modules has an Index property.

You can assign an explicit index number to each of them, or you can leave it 0 which means automatic numbering.

After that if you connect the nodes to an Indexer Node, you can control their transformation and appearance from a single central place, via the Indexer Node.

The Positions property receive a vector in which each value triplet represents a position for the corresponding object. The first three value is the position for object #1, the second three value for object #2 etc.

The same goes for Rotations and Scales properties.

Vertex Colors is similar, but takes four values (RGBA) per object colorizing the objects . Note that this feature only works if you use Vertex Color capable shaders.

Shader Indices is usable if you connect Shader Arrays to the objects instead of a single shader. Each value in the vector determines the index of the shader for the corresponding object. Note that you can use different Shader Arrays for different objects if needed.

Actives can contain 0s and 1s to controlling the visibility of the corresponding objects.

Note that you can assign the same index number to multiple objects. In this case these object will take the same values from Indexer Node.

Indexer Node was added primarily for helping to control objects via a script, but of course you can obtain the values from data files as well, or you can generate them in other ways.

Here is an example:
https://mab.to/9eUYG0b9W
(it will be included in Tutorials in the next release.)

We used this technique in this virtual set, where the cubes on the wall were animated by a script:
https://youtu.be/KwepZCQkV64?t=22