Progress bar updating based on loading (Loading screen)

I assume there must be a float value that keeps track of the percentage of the current level load. I want my progress bar in my widget to update in sync with the level being loaded (Level load screen with progress bar). So, I am assuming a flag is being set when the level is loaded enough to be rendered/opened. So, It seems that a flag is being set when a certain percentage of the level is loaded into RAM? I wonder is there is a variable I can reference that keeps track of level load progress so I can hook this up to my progress bar/animation…

Any idea on how to update a progress bar based on level load progress?
Thanks!

Here is how to accomplish this since 4.20.x,