Replace The xxxxxx With New User:

sudo /usr/sbin/useradd --groups sudo -m xxxxxx

Replaced xxxxxx With New User Password:

sudo passwd xxxxxx

Change Root Password If Needed:

sudo passwd root

Next Lock User Pi "Replace Pi User If Locking A Different User Name"

sudo passwd --lock pi

Now You Can Log Into The Pi Using The New Username.
This Does Not Delete The Pi Folder From The Raspberry Pi.