Hello Yvonne,
The Facing Value Map is defined in "OpenPlant_Catalogue.01.04.ecschema" located at "\\WorkSpace\OPModeler\schemas".
Open this schema in Class Editor, and supplement it with "OpenPlant_Catalogue_Supplemental_Mapping_Modeling.01.04.ecschema" in your project's schemas folder.
You can add new facings or map your custom facings to existing ones.
Hope this helps.
Mehreen