When editing one view of a cell, there are a set of commands in the View menu that will switch to an alternate view of the same cell.
When editing cells with text-only views, the window becomes a text editor. You may then use the Text Cell Context... command (in menu File / Export) and the Text Cell Context... command (in menu File / Import) save and restore this text to disk. See Section 4-10 for more on text editing.
The commands to edit another view work only when that cell exists. To create a new cell of a particular type, use the Make... commands of the View menu. Thus, Make Multi-Page Schematic View... creates a new page in a multi-page schematic. Make Icon View creates an icon from a schematic (see Section 3-11-4 for more on this).