A new UI-based Power Automate flow Connector specifically for PVA has been deployed on Power Automate portal. This is a no-code, UI-based Connector which means that no JSON coding required now to make your flows work with Power Virtual Agents.
Please refer to the Blog post for the details:
Use Power Virtual Agents Connector to build Power Automate flows for your bot
The documentation was also updated to reflect the changes:
https://docs.microsoft.com/en-us/power-virtual-agents/advanced-flow
Note that the flows currently using HTTP Request/Response Power Automate Connector will continue working with Power Virtual Agents.