How to setup a brightness trigger?

I am trying to set up a condition like this:

If bulb A’s brightness is 100%, then turn bulb B on, else turn B off.

Is this possible by using CoRE or others?

I don’t use CoRE but I do use webCoRE all the time.

You can absolutely set this up on that platform. There’s a command for Level which you could check and then act accordingly.

There is also a community created app available on the forums. (Dim with me)
This app will set brightness levels base upon a switch or a bulb brightness + ON state.