I see 2 possibilities in Visual Overview:

• Dirty solution: Put a shape with the color of your background over your parameter control, so as to hide the text and value from it. This is a bit dirty because it requires your background to be the same everywhere (eliminating theming for instance) and the aspect ratio might mess up your visualization if you're not careful.
• Clean solution: Make a SetVar shape in which you can enter the value to set your parameter to and then add a button that does a parameter set with the variable as input. For more info, see Linking a shape to a SET command