There are multiple efforts happening internally to demonstrate Composer working against a CI/CD pipeline. As far as interop between v4 waterfall dialogs, custom code, and Composer built dialogs, see this document describing the process to achieve this: https://learn.microsoft.com/en-us/composer/how-to-add-custom-action
Here are some video resources available to share:
5 minute intro: https://www.youtube.com/watch?v=g8ck1hcTTJk
20 minute getting started video: https://www.youtube.com/watch?v=r9WQPSaLnaU
20 minute advanced language modeling: https://www.youtube.com/watch?v=wG8emu4v6hk
Build an end to end Weather Bot (slightly outdated): https://www.youtube.com/watch?v=ZNcfIgO8biw