This is by design, it's hidden for a reason. You could create 2 variants of the screen and depending on the action show the screen with the prefilter hidden or visible.
But then it would mean that all the prefilters will be hidden when adjusting the screen type. Which is not what I want.
Why am I doing it this way?
Well, I need a filter form for dates in Universal GUI (which is not supported. Only supports text and numbers). So now I created a task for the user to enter a date for the filter, which will be picked up by the prefilter (activate prefilter using process flow).
You can create a variant of the subject and choose which prefilters to have off, on and hidden. No need to change the screen type for that.