Nondestructive tools such as Modular Avatar and VRCFury create parameters and merge expressions menu assets dynamically at build time. As a result, it's often necessary to edit VRC Expressions Menu assets when no avatar in the scene has the associated parameters defined. This was possible in prior versions of VRCSDK, but in 3.7.0 the error in the screenshot is shown and changing the value of the control isn't possible without using the debug inspector. (Previously there was a warning, but it was still possible to change the value)