Taken from the handbook: "With KDE, the settings are stored in .config/kid3rc, the application state in .local/share/kid3/kid3staterc. As a Qt™ application, this file is in .config/Kid3/Kid3.conf. On Windows®, the configuration is stored in the registry. on macOS® in a plist file." Have Kid3 save configuration settings in an ini file rather then the registry. Migrating settings between Linux and Windows will be a breeze. Currently settings have to be entered fresh into a new Windows installation - probably will have to be redone on reinstallation.
This is already possible by passing "--portable" as a command line argument or by setting the KID3_CONFIG_FILE environment variable, see https://invent.kde.org/multimedia/kid3/-/issues/304.