What if I only want to round a couple corners on my rectangle?
You could draw those rounded corners by hand with the Pen tool, or combine two separate boxes using InDesign’s pathfinder tools. But that’s kind of time consuming. Instead, it turns out there is an easy solution in the built-in script samples that Adobe provides.
Pull up the Scripts panel by choosing Window > Automation > Scripts. Look in the Application Samples and you’ll find a script named CornerEffects. Select a box and double-click on this script. You’ll be presented with a (somewhat clunky) dialog that lets you apply the rounded effect to specific corners.
Our friend James Dempsey at The Graphic Mac has a good write-up:
The Graphic Mac: Creating rounded corner boxes easily with InDesign scripts.