I know I'm gonna reply a 6 months topic, but it could still be useful for other people.
So, There's actually a way to get this effect. Funny thing is that I had this idea just cause of this topic, but I then totally forgot about it.
Anyway, here's the solution.
Tweak: Reducing every shaders intensity / opacity
Some Shaders allows you to edit their Intensity by playing with their settings, some others don't.
Though there's not an official way to "reduce shaders opacity" through ReShade interface, I managed to achieve this by making some tweaks.
Basically we'll use a mask for a specific shaders and we'll make it cover the entire screen.
First of all you'll need the effect UIMask to be present in your Shaders Folder ( Game Directory > reshade-shaders > Shaders ), so check this Shader during ReShade installation.
UIMask shader comes with a sample texture called UIMask.png, located in the Texture Folder ( Game Directory > reshade-shaders > Textures ). Open this one with an image editor software and fill it completely with Black ( or download a full black image from google and rename it UIMask.png, after all it's the result that counts ).
Once all's set, launch your game, open ReShade interface and drag your interested Shader between UIMask_Top and UIMask_Bottom. In this way it will limit its effectiveness just to that specific shader (watch the image below to see the load order).
To increase or decrease the opacity, just move the slider "Mask Intensity" as you want.