The expression editor has a "Description" box which is great for displaying documentation about functions.  I'm proposing that this box could also display the description of the input parameter you're editing.

In the attached screenshot, I've hovered over the "Advanced Options" input parameter on the Calendar block.  When hovering, I am able to see great documentation about how to use this input.  However, this information isn't displayed in the "Description" box inside of the expression editor.  This forces me to keep hovering over the input repeatedly to fully grasp the message - fighting it as it repeatedly disappears.

Thanks