When you create a new user account in Windows 11, the operating system (OS) automatically creates a new user profile folder in C:\Users\Username. However, this default user profile folder name is not always what you want.
Windows, by default, will use the first five characters of your user account name as the profile folder name. If you don’t like the user profile folder name, you can change it using a registry hack. Here we show you how to change the name of the user profile folder in Windows 11.
Source: How to Change the User Profile Folder Name in Windows 11