Suddenly this error came and displayed on the left panel. Why is this happening in Production org? Is this a Salesforce bug? Somebody in the Salesforce testing their usecases? Any thoughts?
Looks like it is reported as Known Bug on salesforce due to beta app named 'Dev Hub'. Please look at the following link.
Currently there is no workaround for that. This is a cosmetic unexpected behavior that only appears in the Setup menu. No functionality is broken as a result