Advanced Meshing > Add Hole displays the following dialog.
It allows you to add a hole to a mesh region. You must first select beams as the boundary (closed polygon) of the hole. You have the option to deactivate the selected beams after the hole is created. This ensures that the selected beams will not be part of the structural model. Later, you can select all inactive members by Create >Select by Properties > Select Inactive Elements and then delete them if necessary.