Enable or Disable by setting the parameter:

sprite.material.set_shader_parameter("enabled", false)

This is achieved using a shader.

shader_type canvas_item;

uniform bool enabled = true;

uniform bool weighted = true;

void fragment() {
    if (enabled) {
    COLOR.rgb = mix(vec3((COLOR.r + COLOR.g + COLOR.b) / 3.0),  
        vec3(0.299 * COLOR.r + 0.587 * COLOR.g + 0.114 * COLOR.b), 
        float(weighted));    
    }
}