Since you'll have to work with haikuporter and recipes, you'll have to have successfully worked on a welcome task "INSTALL HAIKUPORTER AND THE HAIKUPORTS RECIPE DATABASE" or any other recipe creating task.

Create a new patchset with haikuporter for games-puzzle/lmarbles to write all its settings, highscores etc. in B_USER_SETTINGS_DIRECTORY. Currently it's using a .folder in /boot/home and maybe other locations.

Create a pull-request for the haikuports repo with your changes.