This is Lawnjelly's Smoothing Plugin modified to work with Godot 4 to help fix Jitter
Here is their initial plugin that as of the time of this writing (11/8/2023) did not work with Godot 4 just Godot 3 https://github.com/lawnjelly/smoothing-addon
I modified it to work with Godot 4 by changing syntax. I do not have the expertise to validate that the changes are entirely working, and though I made the changes to the 3d, I have not tested it there. I have no expertise to modify the code so if it is not working for you, you will have to look elsewhere for help.