You're not the only person who has complained about the loss of the darn-helpful "Save As..." feature in Mac OS X that Apple foist upon us without much warning or ability to vote that we'd like to have it back. No hidden option in the System Preferences, no check box in utility application preferences, nothing. Then OS X Mountain Lion has a sort-of solution, but frankly I don't want to remember the Option key and, quite frankly, having to remember to push the Option key doesn't seem much like "The Computer for the Rest Of Us" or "Think Different". More like "Don't Think It Through".

The good news? With a bit of monkeying with the Keyboard System Preferences you can restore "Save As..." to a significant number of OS X applications. It's easy, you can do it.

Let's step through it together...

Before we start, here's the "File" menu from TextEdit, just as a reference:

Now, let's fix it! Launch System Preferences... from the Apple menu. In the middle of that Window, look for "Keyboard":

Click on it (and yes, you've probably never gone near it in the past. That's alright, time to learn something new, right? :-) then make sure you're on the "Keyboard Shortcuts" tab:

Notice that you need to select "Application Shortcuts" on the left side, then you can optionally click on the tiny black triangle adjacent to "All Applications" to minimize what's displayed, as you can see I have done.

Ready? Here's the fun part.

Click on the "+" symbol because we'll need to not only add "Save As..." but also redo the keyboard shortcut for "Duplicate" too, since we can't just make it vanish. To do that, just assign it the Command-Option-Shift-D key sequence, and name it "Duplicate", like this:

Note that you need to get the capitalization of the words exact for this to work, so "duplicate" is not an acceptable alternative.

Got that exactly like what I show here? Click on "Add".

Now click on the "+" again to add the "Save As..." window. But here's what's important: not only do you need to get the "S" and "A" capitalized exactly as I show, but you need to use a proper ellipses symbol, not just three dots. To get that character, use Option-; (in other words, hold down the Option key and press semicolon).

Then make the keyboard shortcut Shift-Command-S for this feature. Like this:

Click "Add" again and you're done. You can quit System Preferences. Really, that's it.

Now let's go back into "TextEdit' and, hallelujah, look what's shown up:

That's the trick. If you have problems, go back and make sure you have the capitalization correct and that you're using the special ellipses symbol (Option + ;), not three periods.

Hat tip to TJ Luoma over at TUAW for his article on this very subject that served as the basis for this particular Q&A.