In a Brave Browser New Window, go to: brave://version and scroll down to Profile Path.
IF you have not changed the Brave Browser user Profile names, THEN:
Profile named “Profile 1” ← its data is in folder named “Default”
Profile named “Profile 2” ← its data is in folder named “Profile 1”
Profile named “Profile 3” ← its data is in folder named “Profile 2”
etc.
That pattern applies to all Brave Browser Linux OS, MacOS, and Windows OS users.
NOTE: The intial BB user’s Profile named “Profile 1” is the default Brave Browser (“BB”) user Profile created during the original installation of BB. The path to that initial folder named “Default”:
C:\Users\[UserName]\AppData\Local\BraveSoftware\Brave-Browser\User Data\Default
In the path to your user profiles’ folders, notice the “User Data” folder? Back up that folder to a place on your computer that IS NOT somewhere within the installation paths of Brave Browser.
Also back up that “User Data” folder to an external drive. So, you will have 2 backups, and each is in a different location that again, IS NOT within any installation path of the Brave Browser on your Windows OS PC.
Re the brave://version findings, notice the Profile Path ← please report that, here, at your Brave Community issue (substituting “username” for your actual Windows OS user account’s name).