Custom property created with python isn't accessible until I click on the property in the viewport [closed]

Question

I wrote a script that creates a custom property in the World panel. It then creates a driver on the object color that's driven by this custom property, but it doesn't recognize the data path as valid until I interact with the custom property slider in the viewport.

I have tried code to redraw all UI panels, among other things. Clicking the "update dependencies" button doesn't work. Nothing seems to make the custom property accessible/visible to Blender except interacting with it and then clicking in the driver so the data path is magically recognized as valid.

I need the custom property to exist on the World panel in the UI, with the slider, exactly as shown. I realize there are other ways to create custom properties, but I need this specific result for my workflow.

The problem:

My code:

import bpy

context = bpy.context

# Create new custom prop 
new_custom_prop = "test_prop"

context.scene.world[new_custom_prop]=1.0

my_world = context.scene.world
id_props = context.scene.world.id_properties_ui(new_custom_prop)
id_props.update(
                soft_min=0,
                soft_max=1,
                )

obj = context.active_object

# Add drivers to object color
d = obj.driver_add('color',0)
d.driver.type = "AVERAGE"

var1 = d.driver.variables.new()
var1.targets[0].id_type = 'WORLD'
var1.targets[0].id = context.scene.world
var1.targets[0].data_path = "[\""+new_custom_prop+"\"]"