You can create permanent and temporary reference planes in different ways. As soon as you create a reference plane, it becomes the active one used by Ref and Plane modes.
To create a permanent reference plane
Select an object, or one or more components. If you select multiple components, the reference plane is based on the average reference frame.
Choose Transform Reference Planes Create Reference Plane from the Transform panel. A permanent reference plane is created named ReferencePlane by default, and its property editor opens.
Press Ctrl+dash (Ctrl+-). A permanent reference plane is created named ReferencePlane by default, but its property editor does not open.
To create a transient reference plane based on the current selection
Select an object, or one or more components. If you select multiple components, the reference plane is based on the average reference frame.
A transient reference plane is created based on the selected element. The previous transient plane is "forgotten."
To pick a new transient reference plane using a specific selection filter
Right-click on Ref or Plane, then choose one of the following:
Pick Object Reference lets you pick an object with the Rectangle selection tool.
Pick Point Reference lets you pick one or more points with the Rectangle selection tool.
Pick Edge Reference lets you pick one or more edges with the Raycast selection tool.
Pick Polygon Reference lets you pick one or more polygons with the Raycast selection tool.
Pick an element. If you are picking a component type, you can first pick an object (if it is not already selected), then pick components on that object. A transient reference frame is created based on the element you picked.