You can store any data inside the marker.
The easiest way to do this is:

marker["myKey"] = myValue;
...
ValueType value = marker["myKey"] as ValueType;

Example:
https://infinity-code.com/atlas/online- … ample.html

From what I can see, a marker has two main fields: the location, and the display label.  Is there any way to store additional (unseen) data in the marker?

For example, if I want to create markers from a Google Places search, each Google place has a unique places_id so it's easier to reference.  Is there a way for me to store that in the marker, so I can recall it later during an OnClick (or other) event?

Thanks in advance for your help!