Users add customization to OpenPlant_3D.01.08.ecschema.xml and other Supplemental schemas. They want to have one separated schema where will be available option to create new classes and properties and not change initial schemas. This will help to easily update customization from version to version. Now you need to compare schema and move new classes and changed properties from version to version. It took very long time. Users even do not want to update OPM to new version because of this schemas limitation.