OK - I have done some further investigation and found out that I can disable the support button by disabling co-browser support setting in Pega Express - Settings - Behaviour.
New issue that I am facing is that when I am going on Behaviour page - I am not able to make any changes. I see "Changes are not allowed at this time. Please contact your system Administrator". Any clue on what role I should add to operator profile?
I don't know, but often when I see an error I don't understand, I use the Pega tracer to understand what logic was performed that concluded that an error should be shown. Often that gives me knowledge of how to solve the error.
thanks for your response! I managed to hide the support button by making changes to the js file that loads firefly components. Though its not a rightway, I have raised a service request to ask for a fix. As per design, there should be a check to see if "EnableCoBrowse" is set to true and if it is only than Pega Co-Browse (support) button should be loaded