Can someone help me?about Godot GPU particle System,How to make my shader custom parameter into a curved form that is controlled based on particle life duration?

Help
1

Godot Version 4.6.3

How to make my shader custom parameter into a curved form that is controlled based on particle life duration? I can not find any custom data slot.
If I write a texture dissolve in my shader, and I want to be able to make that dissolve level go from 0 to 1 asymptotically over the life of the particle, there are a lot more custom parameters like that, but what annoys me is that I haven’t been able to find any way to do this at all.
2 
uniform float dissolve_value : hint_range(0,1);
3

You can get the lifetime information from INSTANCE_CUSTOM in the vertex function

shader_type canvas_item;

uniform sampler2D dissolve_texture;

varying float lifetime;
void vertex() {
	lifetime = INSTANCE_CUSTOM.y;
}

void fragment() {
	float noise_sample = texture(dissolve_texture, UV).r;
	COLOR.a = min(COLOR.a, step(lifetime, noise_sample));
}