Hi,
The property should be specified by the automation tool you use. From what I can understand, the extension is being installed by policy in Azure Policy. In this case the policy is using ARM Template to apply the extension. If you are using built-in policy and you do not see option to provide the value when you assign the policy best is to clone the built-in policy definition and modify it according to your needs. Here you are able to see example how the property stopOnMultipleConnections is being used in ARM template deployment. You will have to add the same property and the value that you desire in the cloned policy definition. After that you save the definition, and you can do policy assignment with it. If you are using custom policy definition you can already edit it and add the property.
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