Keith
Going a bit from memory as it's been a few years since I had mine off but on the boat now and refreshing memory.
Lower blinds and tilt them. Look up with flashlight and you should find a few 3-4 visible flat head screws inboard of the blind header.
If I recall correctly the end fittings and a center support typical of that type of blind is attached to a board, wider than the blind, and that inturn is screwed up into the valence above all the windows.
There isn't enough room to open the typical end fittings when up in place and I think is the reason for the extra board.
It helps to have another pair of hand to hold at least one one of the assembly while removing and almost essential to get it back in place.
I was ready to give up on mine but after removing and replacing a couple of parts avail from mfg they raise / lower much easier.
I wish the raise / lower and tilt were at opposite ends to prevent the cords tangling but having them raise w/o jamming helps a lot.