Trying to animate custom bone like scarf get this error/warning not all bones/transformation in this project is available in the game object?

Hi dev,would love to animate with humanoid my scarf with custom bones from the main armature.But the above warning come up and in the config mode there are error/warning"the are rig configuration where the appropriate joint/transform cannot be found.

Can i get a step by step on how to use custom bones in humanoid rig?Thanks