You can now remove cost quantities in bulk.

src/blenderbim/blenderbim/bim/module/cost/operator.py

@@ -341,11 +341,19 @@ class UnassignCostItemProduct(bpy.types.Operator):
 
     def _execute(self, context):
         self.file = IfcStore.get_file()
+        if self.related_object:
+            products = [self.file.by_id(self.related_object)]
+        else:
+            products = [
+                self.file.by_id(o.BIMObjectProperties.ifc_definition_id)
+                for o in bpy.context.selected_objects
+                if o.BIMObjectProperties.ifc_definition_id
+            ]
         ifcopenshell.api.run(
             "cost.unassign_cost_item_product",
             self.file,
             cost_item=self.file.by_id(self.cost_item),
-            products=[self.file.by_id(self.related_object)],
+            products=products,
         )
         Data.load(self.file)
         bpy.ops.bim.load_cost_item_quantities()

src/blenderbim/blenderbim/bim/module/cost/ui.py

@@ -309,11 +309,14 @@ class BIM_PT_cost_item_quantities(Panel):
             "active_cost_item_product_index",
         )
 
-        row = self.layout.row(align=True)
+        row = self.layout.row()
 
         row2 = row.row(align=True)
         row2.prop(self.props, "quantity_names", text="")
-        op = row.operator("bim.assign_cost_item_product", text="", icon="ADD")
+        op = row2.operator("bim.unassign_cost_item_product", text="", icon="REMOVE")
+        op.cost_item = cost_item.ifc_definition_id
+        op.related_object = 0
+        op = row2.operator("bim.assign_cost_item_product", text="", icon="ADD")
         op.cost_item = cost_item.ifc_definition_id
 
         row2 = row.row(align=True)