Multistate documentation

[ITensEI]

The plugin offers regular and multistate options, however there's no documentation on how to use it. In NodeRED when I press the button the payload.payload.isInMultiAction is showing false however it does add the state variable with value 1 when the 1st option (left) is selected and 0 when the 2nd option (right) is selected. Is that a bug?

In NodeRED I'm seemingly unable to set the state of the button dynamically. I have a binary sensor that when ON I want 1st state to show and when off the 2nd state. When setting it to trigger on the willAppear event the state doesn't change and remains on the state I left it at when pressing the button manually. How do I change the state dynamically?