in the IFC structure of the model, you can see the entities and their subentities such as IfcOpeningElement.
Under each of the walls or slabs, you can have connected “holes” – opening elements (IfcOpeningElements).
To view all IfcOpeningElements at once and see the volumes you can use the Objects Info plugin.
The tool Group (Objects Info) allows you to select the feature because of which elements will be divided into separate group.
If you want to see all IfcOpeningElements use the tool Group and as a feature choose from the list the IfcEntity.
In the bottom of the window of the tool you will see the content of the model grouped by IfcEntity. You will see there also “IfcOpeningElements”.
You can click on the group and select all of opening elements in model to view them.
You can also see each of the opening elements by expanding the list and clicking one by one. While you doing you can see the chosen entities in the IFC Structure and also you can display them in the model space.