Parameters added using the "Advanced Options" option on a portlet config do not appear to be accessible in the PortletRequest. I added a parameter using the "Advanced Option" and that parameter value was not present when retrieved in the PortletRequest. This thread in the user forum tracks the steps taken: https://web.liferay.com/community/forums/-/message_boards/view_message/91616693
Happy to provide more information if needed. Should be easily reproduceable. Parameter passed in URL works fine.