Google Ads has a new column named "conversation started" for message assets, like WhatsApp messaging, through Google Ads. Clicking on a WhatApp button in Google Ads will trigger the "conversation started" metric in Google Ads.
This was spotted by Arpan Banerjee, who posted about it both on LinkedIn and X, he wrote, "Google has rolled out a fresh conversion action: "Conversation Started" and shared this screenshot of the report:
Ginny Marvin, the Google Ads Liaison, confirmed this as being new and posted on LinkedIn saying, "Yes, confirming that you’ll see this when using message assets. A click on the message extension on your ad results in a message sent, and Google will report a conversation was started."
Google Ads has a more detailed help document on message assets over here.
Forum discussion at LinkedIn.