How to permanently unhide the Users Library folder in Catalina
There's a visible pref for it, no need to dig in defaults

This is simplest if you use Icon or List view*

Open to your User's Home folder - /users/[yourname]/ -  then either View Menu > Show View Options or  Cmd ⌘   J 
Check the box for Show Library Folder.



*This is just because in Column view you're less certain exactly which folder you are affecting. The Show Library option only appears when you're in exactly the right folder.