There is a great site to look at details of things like this:
https://catalog3d.winnebagoind.com/menu/Parts.htm
Interactive that takes a bit of play to get good at using but great for details without crawling around as we can "see through walls"!
I think this is the correct shade?
Click to get best view!
It looks like an angle with screws I marked in green will get the valance down, but it may only need to remove the shade?
There are metal spring clips along the top metal of the shade. Grooves on front and back where small folds are made in the clips to snap into the grooves?
I expect there to be tabs sticking out front to press up. Pretty hard possibly!
AS that tab is pressed up the front of the clip should come out of the groove to rotate the shade fornt down and relaese.
I find going back harder but if I put the rear into the groove and then rotate the front up, it will eventually snap back into place. I expect a fight as it seems to take a lot of force to get it up and snapped!
Maybe a rubber mallet to whack it!