We are looking to monitor PVST on Cisco Catalyst Switches.

By default, Cisco only allows access to the default VLAN instance of the BRIDGE-MIB.
For accessing the other available VLAN instances, one can append the vlan number after the community sting, e.g.: 'public@25' would return the data for vlan 25.

Therefor, it would be useful if we could append the VLAN ID to the community string via a discovery macro. For instance:

{$SNMP_COMMUNITY}@{#VLANID}

For SNMPv3, it is possible to achieve the same by assigning a different context to a user. In this case it should be possible to override SNMP context on the item level.

However, we need a way to assign these SNMP parameters to the item. In the past it was possible to change SNMP parameters per item, but that has since been moved to the host interface. Can we allow a override of the SNMP parameters on the item level for these kinds of use cases?

See here for more information on the subject:
https://www.cisco.com/c/en/us/support/docs/ip/simple-network-management-protocol-snmp/40367-camsnmp40367.html

ZBX-9666 also refers to some kind of SNMP Community String Indexing.