How can I modify built-in packages?

I have recently faced a bug in a Unity package, so this was the fastest way to fix it and continue the work. Yeah obviously you lose new updates but there is a way to create some sort of a patch tool, that would update the local package and apply your changes. Of course, this is unnecessary if the issue is fixed in an update. If you already know a tool that does it, would be great if you shared it in the comments.

https://support.unity.com/hc/en-us/articles/9113460764052-How-can-I-modify-built-in-packages-

#package #upm