Instead of mixing two strings into a GList, use a PurpleKeyValuePair.

Use struct initializers and G_N_ELEMENTS.

Rename lv to choices for clarity.

Change from PurpleRequestFieldList to PurpleRequestFieldChoice as we don't need multiple selection.

Opened Finch, opened Preferences, saved them, and exited Finch. Re-opened Prefs and confirmed they were saved and as expected.