can you submit DMCA claim to them?

I don't need to since my request was a simple way to remove multiple videos at once, or have an option to not save my stream as videos.

I can delete the videos one by one though, it's just a lot of work, especially when the connection is flaky (it produces a ton of videos in that case)

Doubt it. Their T&C probably protects them from that kind of thing, but I can't even find it on their site right now.

2.Except for Broadcaster Content already downloaded by users, the foregoing license granted by you terminates regarding a specific piece of Broadcaster Content once you remove or delete that Broadcaster Content from the Livecoding.tv Service.

-- From Livecoding T&C https://www.livecoding.tv/terms/

seems from the T&C you should be able to remove or delete videos