is the reimplementation of light shader's shadow_vec possible?

[just-wasted]

In Godot 3.5 it is possible to manipulate shadows with the canvas_item shaders light{} builtin shadow_vec (inout). In Godot 4 this is no longer possible. Could this be reimplemented in the not so far future? I think its really useful to create good lighting on sprites which represent vertical/ elevated entities of the game world.

[AThousandShips]

How does this differ from the SHADOW_VERTEX in the fragment stage?

[just-wasted]

Since i'm new to shaders i don't know how this would differ. Playing around with SHADOW_VERTEX works well for sprites in top-down projection when setting SHADOW_VERTEX.y. to the distance from viewport-top to lower end of the sprite.

As far as i can tell from my limited experience, using this approach on isometric sprites seems not the way to go.

In the Godot 2.1 isometric lighting demo LIGHT_VEC was used to correct shadow on walls. This didn't work on Godot 3 but SHADOW_VEC got introduced to help with this.

[AThousandShips]

Does the LIGHT_VERTEX work? Also have you tried utilizing the z component? Have you read the documentation?

[just-wasted]

LIGHT_VERTEX doesn't seem to have any affect on shadows. z in 2D is only relevant in combination with normal maps, as far as I know.

I've read the documentation, but i have no clue how exactly SHADOW_VERTEX works and if it can be used for my use case. From my understanding it can be used to a) move the shadow map, b) set the shadow for x or y direction from a specified sample point in screen space, like i did in the first image.
I've looked around the demo projects but didn't find one for SHADOW_VERTEX or VERTEX. Most fragment shaders I've found seem to only use COLOR.

[just-wasted]

update: #8339 (comment)