You can now specify relationships to IFC Diff in Blender

src/ifcblenderexport/blenderbim/bim/operator.py

@@ -1147,7 +1147,8 @@ class ExecuteIfcDiff(bpy.types.Operator):
         ifc_diff = ifcdiff.IfcDiff(
             bpy.context.scene.BIMProperties.diff_old_file,
             bpy.context.scene.BIMProperties.diff_new_file,
-            self.filepath
+            self.filepath,
+            bpy.context.scene.BIMProperties.diff_relationships.split()
         )
         ifc_diff.diff()
         ifc_diff.export()

src/ifcblenderexport/blenderbim/bim/prop.py

@@ -921,6 +921,7 @@ class BIMProperties(PropertyGroup):
     diff_json_file: StringProperty(default='', name="Diff JSON File")
     diff_old_file: StringProperty(default='', name="Diff Old IFC File")
     diff_new_file: StringProperty(default='', name="Diff New IFC File")
+    diff_relationships: StringProperty(default='', name="Diff Relationships")
     aggregate_class: EnumProperty(items=getIfcClasses, name="Aggregate Class")
     aggregate_name: StringProperty(name="Aggregate Name")
     classification: EnumProperty(items=getClassifications, name="Classification", update=refreshReferences)

src/ifcblenderexport/blenderbim/bim/ui.py

@@ -1132,6 +1132,9 @@ class BIM_PT_diff(Panel):
         row.prop(bim_properties, "diff_new_file")
         row.operator("bim.select_diff_new_file", icon="FILE_FOLDER", text="")
 
+        row = layout.row(align=True)
+        row.prop(bim_properties, "diff_relationships")
+
         row = layout.row()
         row.operator('bim.execute_ifc_diff')