CAD tip # 7953:

There is no predefined AutoCAD keyboard shortcut for this, but you can add your own.

Start the CUI editor and use the "star with an asterisk" button to add a new command. Name it e.g. "PaperModel" and use the following DIESEL command as its macro:

^C^C^P$M=$(if,$(=,$(getvar,cvport),1),._mspace,._pspace);

Now go to the CUI section Keyboard shortcuts > Shortcut keys and mouse-drag here your PaperModel command from the command list. On the right in the Properties > Access > Hotkey, assign the requested shortcut to this command, e.g. Ctrl+Alt+P. Finish the CUI dialog.

Now you can toggle model/paper spaces in your layouts just by pressing Ctrl+Alt+P.