User-defined planes visible in the drawing

Problem

"I have created a new plane in the plane system, but I can't get it to appear in the drawing."

Solution

Only the planes that exist at the time the drawing is created are saved with the drawing. Therefore, if you add new planes to the plane system later, they will not automatically be available when you open an existing drawing for editing.
To make the new planes available in an old drawing, go to Drawing mode and select View → Planes dropdown menu → Restore default plane definitions.