Document SNMP oid varbind pattern matching and varbind expansion to create unique events

I am looking for some definitive documentation on configurations using eventconf.xml. In particular I am interested in snmp trap mapping. The old fairly simple information on the OpenNMS wiki about oid mapping appears to have gone and there is nothing in the docs to replace it. (https://docs.opennms.com/horizon/29/operation/events/event-configuration.html)

Looking directly at the eventconf.xsd https://github.com/OpenNMS/opennms/blob/develop/opennms-config-model/src/main/resources/xsds/eventconf.xsd
I have a lot of questions about the supported functionality. I have tried to work through the eventd code to work out what is going on but it is complex and I certainly can’t point a customer at it.

Any documentation for these would help:

There is a line in eventconf.xsd under the mask element documentation ‘XXX need to add information about varbind’
I need to know more about how varbinds are processed and can be used for pattern matching to create unique events.
There is also a new feature https://issues.opennms.org/browse/NMS-10626 varbind expansion which also appears to not be documented.

I am also wondering how the following tags are intended to be used. There are no examples I can find.
<element name="varbindsdecode">
<element name="filters">
<element name="forward">
<element name="parameter">