How do I export a IFC2x3 out of BlenderBIM? ATM for me it exports to IFC4 only.
In the scene properties, under Model View Definitions panel at the bottom, there is a drop down to select IFC2X3.
Keep in mind that to export IFC2X3, you need to yourself ensure that all your elements comply with IFC2X3. It won't "magically downgrade" for you. If you have an IFC4 object (e.g. an IfcWall with a predefined type) it will error out.