Wii - where is the sdcard

Some (homebrew) games need to be located on the sdcard for working correctly, for example

On dolphin, it is possible to set where the sdcard is located and change other settings, I currently do not seem to be able to find similar option in the retroarch core.

Does such option exist? Either in the gui, or by modifying the configuration file directly? If not, does retroarch use a predefined location as sdcard for the wii core? If not, is there any way to play such games with retroarch?