Prerequisites
A BIM Property Group and Property Set exist under your manufacturer module.
Steps
1.) Add your individual properties. Add rows to L_BIMPropertyTab for each property that belongs to your new property set.
2.) Set the property's mode and display order. Use BP_MODE to define the property more specifically, and BP_IX to control the order your properties are listed in.
3.) Set the property's value type. Use BP_TYPE to define what kind of value the property holds.
Tip - Mapping a property directly to an IFC type: BP_DESC accepts a special syntax, IFCTYPE = <ifctype>, that determines the property's target IFC type in exported IFC files. For example, IFCTYPE = IfcPositiveLengthMeasure creates an IFCPOSITIVELENGTHMEASURE property in the IFC export. Use this when your custom property needs to map to a specific IFC property type rather than exporting as a generic value.
Result
Your property set now has its own individual properties, each with a defined mode, display order, and value type — and, where needed, mapped directly to a specific IFC property type.