Hi,
try to layer a disconnected knob without function, optionally with a transparent (0% opacity) image, over the areas that you do not want to be reachable. Remember that the dummy knob needs to be below the envelope in the GUI tree to be above. The tree inverts it kinda…
I only tried this with a knob. You might find other elements to be better suited. Afaik images alone are not blocking clicks.
Hope this helps