To set up a custom webhook connection in Mixpanel, you need to follow these steps:
1. Navigate to the Integrations UI in Mixpanel.
2. Add a new Webhook connection.
3. Provide a name for the connection and the URL of your webhook server.
After setting up the webhook, you can sync any cohort to this connection from the cohorts page in Mixpanel. Optionally, you can also set up Basic Authentication when calling the webhook URL provided.
Please note that you need a paid Mixpanel plan, a Mixpanel project, and a webhook server to set up a custom webhook connection. If you want to test the setup, you can create a dummy webhook using a service like webhook.site.
For more details, please refer to the Mixpanel documentation.