Quote - Not entirely sure what it is you want, but try this:

Create a new layer and draw the diamond shape where you want it to be. Fill the shape with any colour.

Set the layer fill (not opacity) to 0%.

Add a Bevel & Emboss layer style and turn on Inner bevel, Smooth, Direction down. Now play with Size, Soften, and the Shading (especially the light angle and altitude) to get the effect you want. You can try other bevel styles if inner bevel doesn't work for you.

I believe the above is the simplest and most flexible way of doing it.

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