In Lion’s Finder, you can group files, folders, and applications in a variety of ways – by name or date last opened, for example or, in the case of applications only, by application category (View > Arrange By > Application Category).

Unfortunately, Mac OS X lumps many types of application into a category called Other. And even when it does group an application more specifically, you might disagree with its categorisation. Amazon, for example, classifies the Kindle app as Reference, while you might consider it Entertainment. Fortunately, you can change the category an application is assigned to or even add new categories of your own.

If the application is running, quit it, and then go to Applications, Control-click (or right-click) on the application in question, and choose Show Package Contents from the contextual menu. Open the Contents folder, look for the info.plist file, and open it in your plain-text editor of choice. (You may be prompted as to whether you really want to unlock the file for editing; assure Mac OS X that you want to do so.)

If your application is already categorised as something besides Other, search for the string – LSApplicationCategoryType. If you can’t find this, or if it’s a previously uncategorised application, you will need to add a new key. (If you do find the string, skip straight on to the next paragraph.)

To add a new key to the info.plist file, skip the first four lines (the last of which should be an XML <dict> tag). On the line below it, insert this line (without any spaces): <key>LSApplicationCategory Type</key>. Press Return. Now type the following:

<string>public.app-category.productcategory</string> (again, without spaces). Then, in that same line, replace public.app-category.productcategory with one of the entries from Apple’s list of approved product categories – you can find the list at www.macworld.com/7558.

Copy the category name you want to specify for your application from that list and then paste it into the info.plist file, making sure that you paste it exactly as it appears in Apple’s list. When you’re finished, save your changes and go back to your Applications folder. If it isn’t already arranged by Application Category, use Arrange By to make it so.

If your application doesn’t immediately appear in the category you specified, you may need to move it out of the Applications folder momentarily and then return it to the folder to make the Finder notice the change. Moving applications in Lion can be tricky, however. Start by dragging the application to the desktop. If, instead of moving the actual application, Mac OS X creates an alias there, hold down the Cmd key and drag the application to the desktop again. Once it has been moved, just move it back into the Applications folder again. It should now appear in the category you specified.