I'm a Claude Code user primarily. The best UI based orchestrator I've used is Zenflow by Zencoder.ai -- I am in no way affiliated with them, but their UI / tool can connect to any model or service you have. They offer their own model but I've not used it.

What I like is that the sessions are highly configurable from their plan.md which translates a md document into a process. So you can tweak and add steps. This is similar to some of the other workflow tools I've seen around hooks and such -- but presented in a way that is easy for me to use. I also like that it can update the plan.md as it goes to dynamically add steps and even add "hooks" as needed based on the problem.