@PhoneBoy is correct. This is per-VS on each gateway. Most likely, you will want your SNMP mode set to vs-direct-access. This lets you poll a VS directly with its VS address, rather than have to go through VS0 and set an SNMP context. Some SNMP managers may have issue with this. However, be aware that SNMP traps always will originate from VS0 with with context for the VS.
#ShamelessPlug
I have published an Ansible method to send CLISH configurations to Gaia hosts, including VSX virtual systems, in the CheckMates ToolBox contest forum. It uses a Jinja2 template to generate the configuration. You can edit the startup script to remove the "clish_cmd" as a CLI argument, and instead define 'clish_cmd' as a YAML list with your SNMP configurations. The VSID will be set automatically based on your inventory configuration. The playbook will also handle your VSX gateway cluster, to deploy the configuration for the VS on all VSX gateway hosts (each node of the cluster). Or, if you just have a single VSX gateway, that will work, too; this is defined in the inventory as well.
This could be helpful if you're looking to automate your rollout and intend to deploy across a large number of virtual systems.