Computer Configuration > Administrative Templates > Google Chrome - Default Settings (users can override)
Both
HKLM\Software\Policies\Google\Chrome\Recommended
Setting the policy changes the default directory that Chrome downloads files to, but users can change the directory. Leaving the policy unset means Chrome uses its platform-specific default directory. This policy has no effect if the policy DownloadDirectory is set. Note: See a list of variables you can use ( https://www.chromium.org/administrators/policy-list-3/user-data-directory-variables ). Example value: /home/${user_name}/Downloads