I tried, but no luck, bro... Thanks anyway!
As this mod doesn't have an extension folder, I created one to try, including the mentioned paragraph but it doesn't work. Tried integrity test, diferent CMS versions, alter some parameters in Showroom CM, but the song remains the same, as said Led Zeppelin...
But looking for diferent fixes in the web, I suspect that the problem perhaps will be in this option...
View attachment 1244606
... but I don't know how to change to "yes"... 🙄
EDIT: Please, do not suffer any more for me. In the end I have been lucky enough to find another version that works more or less correctly, searching the most sordid recesses of the internet... Thank you all.
Oh Ok, sorry, I thought you were looking for the post you couldn't find. But yeah, you were more looking for the solution, not just the post

Mea culpa, didn't think far enough.
You found another car in the meantime, but maybe you want or need to fix it on another car, or somebody else want it....
So, here's something more detailed and hopefully more purposeful, as tutorial.
You were almost there. In the meantime, you have learned a lot. 👍
You did that right, if there is no extension folder, you have to create one in the car folder, then you have to create an ext_config.ini.
Then, when you put the code in there and save it, of course you have to adapt it to the car and its materials or meshes.
Since we don't know the exact car you want to change or better repair, we can only give you an approximate guide, but not the exact code, sorry.
So, you have the mesh name for that mesh: 1111103_SUB0 and the Material name: windowint.
Here´s a new modified code block:
[SHADER_REPLACEMENT_...]
ACTIVE=1
DESCRIPTION= fix missing transparent windscreen
;MESHES =
MATERIALS= windowint,
IS_TRANSPARENT = 1
Paste that into the ext_config.ini and it should work... 🤞
These both links could help to understand the beneath working mechanisms etc., even there are a bit outdated right now.
There are three options to tweak the dirt to your liking, depending on what you want to achieve: To just get rid of the dirt completely, use CSP's WindscreenFX feature If you just want reduce the amount of glare created by the dirt you can use a CSP car config file to tweak the shader...
www.nutrimatic.cc
Some mod cars for Assetto Corsa have a bug which causes weird glare and shadows on the windscreen, and prevents Custom Shaders Patch from being to remove dirt or blur shadows on the windscreen with WindscreenFX. This is how to fix this problem without breaking online compatibility
www.nutrimatic.cc