[Ken Case]

Originally Posted by maz

When I have something grouped together—say the header of a mocked up website—I may want to reuse that group at many places throughout the file. However, if I ever make changes to that group, I’ll have to manually replace each instance with the newly edited one. I was hoping that there existed some feature or workaround such that I could avoid that time-consuming and tedious procedure.

You can get close to what you want by leveraging OmniGraffle's LinkBack support. Copy the shapes as PDF (using Edit->Copy As->PDF), then paste them back into OmniGraffle in several places. The PDF images you paste back in will all refer to the same source objects, and here's the trick: you can double-click on any one of them to edit all of them.

Double-clicking on an image will give you a separate LinkBack source window where you can make your changes, and when you save in that window you'll see all of the images update at once.

It would still be nice to have true shared objects, of course, and that's what the request Brian mentioned is about—but I hope this technique is helpful in the meantime!