transparency - Photoshop, gradient map to transparent? - Graphic Design Stack Exchange
adobe photoshop - Create gradient with transparent edge - Graphic Design Stack Exchange
How to create a "Black to transparent" gradient
How to create transparent gradients?
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Hi all - help would be much appreciated here!
I am trying to create transparent gradients to create light leaks in photos, but on the panel, I only see Reverse and Dither as options. No Transparency option is showing up for me. How do I adjust this setting?
Thanks in advance!
Not quite certain I understand, but... couldn't you simply use a Gradient Fill layer? Layer > New Fill Layer > Gradient...

That gives you the ability to adjust the gradient dynamically, without being restricted to the Layer Style limitations or using blend modes.
How about you apply a layer effect to your foreground shape?
Outer or inner glow set to the dark color would do the trick and be completely editable. Inner shadow or drop shadow could also work if you prefer.