Before Mavericks, to add an item to the sidebar in the Finder, you could drag and drop it or use command (⌘) T. This was pretty easy to remember and easy to perform.
The way this works changed when Apple brought out the Mavericks OS. Simply using the drag and drop approach doesn't work on it's own. You can drag and drop a file into a folder stored in the sidebar however, releasing the file won't add it to the sidebar itself.
Adding an item to the finder sidebar can be done in one of two ways.
The first way is whilst holding down the command (⌘) key you drag and drop the file to the desired location.
The second way is having selected the file in a Finder window, use the keyboard shortcut command-control-T, or select 'Add to Sidebar' from the File menu.
One other way to add an item to the Finder sidebar is to write a small Applescript Application and add it to the Finder window toolbar. Adding a file or folder to the sidebar will simply be a click away, no need need for a keyboard shortcut or a drag'n'drop!
To create an app follow these simple steps.
1. Open up the Applecript Editor. This can usually be found in the Applications folder.
2. Copy and paste the code below into a new script window and compile it by clicking the Compile button. Once compiled it should look like the image of the Applescript Editor window below.
tell application "Finder"
tell application "System Events" to tell process "Finder" to keystroke "t" using command down & control down
3. Select Save As... from the File menu. In the dialog box select Application from the File Format dropdown. Make sure the Run Only, Startup Screen and Stay Open options switched off. Save the Application to somewhere handy.
4. Drag'n'drop the Script Application into the toolbar as shown whilst holding down the command (⌘) key.
5. To add a file or folder to the sidebar select the relevant file, folder or Finder window and then click the application's icon in the toolbar. The item should appear in the sidebar.
6. Now test your new Applescript Application on a few files and folders.