Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Lxss\{your linux uuid}\BasePath
from default to \?\D:\Path\to\ext4.vhdx , then move ext4.vhdx to that path, reboot WSL2, and it seems work well.
default user:
goto /etc/wsl.conf
[user]
default=b14ck0ps