You specify which equipment connections should be displayed on your one-line diagram. This allows you to easily find and insert the large pieces of equipment without having the “Insert One Line Device” dialog cluttered with every equipment connection on your project.
To change this setting, query the piece of equipment. There is a toggle labeled “Show on One Line”. If it is checked, you can insert this equipment on your one-line diagram. If it is not checked, you cannot insert it.
Use the “One Line Diagram->Insert One Line Device” command to insert the equipment connection on your one-line.