You probably know that you can double-click inside a viewport’s boundary to activate and edit the items in model space.
But have you ever double-clicked on a viewport boundary?
If you try it, you’ll see that your screen suddenly looks a lot like model space, except with a diagonal red border all the way around the outside.
What you’ve done is maximized your viewport—you can edit, pan, zoom, etc., and when you’re done you can go back to paper space without having affected the scale or view area of the viewport.
Which brings us to the next logical question: How do you get back?
Look for the red-bordered button on the status bar.
Click it, and it minimizes your viewport, taking you back into the layout. The arrows on either side let you maximize different viewports. The view might not change unless you’ve got viewport overrides like layer color or visibility settings.
For my keyboard fans, the commands for this feature are VPMAX and VPMIN.