From G String dated 15 Feb 2019 post #192 "Rig Manager 3.0 Editor" -
"we support what makes sense from various standpoints. it's not necessary a good idea to start developing something and use deprecated/old technology right from the start. of course, we have no plans to exclude older versions unless we feel that it is necessary. macOS 10.9 is a borderline case, can't promise anything right now. for windows, it will be 8 or higher. there might be a chance that new rig manager version will continue to work with e.g. windows 7 but the editor part will be not visible in this case."