If you have an existing cog search index, then you can use the https://learn.microsoft.com/en-us/azure/machine-learning/prompt-flow/tools-reference/vector-db-lookup-tool?view=azureml-api-2 in the prompt flow instead of https://learn.microsoft.com/en-us/azure/machine-learning/prompt-flow/tools-reference/vector-index-lookup-tool?view=azureml-api-2