Designer: Change layer luminosity without affecting layer below ?

[Cobalt]

Is there a way to lower the top layer's luminosity without affecting the layer below it ?
(In this example the yellow must remain identical, but the tiles must be uniformly darker)

TopLayerLuminosity.afdesign

[lepr]

Yes, there are several ways.

You can nest an Adjustment in the Layer Top layer and it will not affect the Layer Bottom layer which contains the yellow object. For example, an Exposure, HSL, Levels, Curves, etc Adjustment.

Alternatively, since you are already using FX Outer Shadow on Layer Top, also use FX Colour Overlay with semi-opaque black.

[carl123]

Or you could just add a Brightness/Contrast adjustment layer in the "Layer Top" Layer

The "trick" is to ensure that whatever you do it is a child layer of the top layer not above it or else everything will be affected, including the yellow layer

[Cobalt]

ah, that's where the adjustments are 
Thank you @anon2 and @carl123