I was extremely excited to see that repeats were going to be accessible from webhooks in 3.10, but I haven't seen anything showing how to access them yet. I created a survey yesterday in 3.10 that had a repeat to test it out and way the repeat listed in the expected return of the webhook, but upon submission, the repeat information didn't get passed along. I am sure there will be something added to the documentation eventually, but I wanted to see if I could get a little help since I will be setting up some forms soon that would really benefit from accessing the information directly without having to create an additional REST query of the related table to extract it.
I don't believe you need to do anything special to get repeats and images to show up in the webhook payload from the field app. Provided your survey is published with 3.10 and you are using the 3.10 field app, this information will be included in the payload.
How did you create the webhook, are you using Integromat or Microsoft Power Automate, or another provider? If you are using one of the provided Survey123 connectors in the webhook provider, please ensure you are using the latest one, as they were recently updated with 3.10 release to support these new features.
I am using Integromat and created a new scenario based on your comments. The interesting thing is that the repeats show up in the mapping tool, but the response breakout doesn't call out the repeats at all. This was confusing me because you can normally find the arrays in the response of the webhook. Thank you for clarifying this for me!