Prior to version 3.0, TextWrangler allowed you to put the document drawer to the left or right of the main window. As of 3.0, TextWrangler no longer has a preference for this and the document drawer is always shown to the right of the main window. But if you want the document drawer shown to the left you can still get this by using a terminal command.

To do this, you first need to open a terminal window. The Terminal application is found in "Applications" > "Utilities". Once the terminal application is open, enter the following line and hit the Enter key:

defaults write com.barebones.textwrangler MultiDocumentWindows:PreferredEdge -string "Left"

Once this is done, close TextWrangler and restart it. The document drawer will now be on the left. If you want to put it back on the right, you can repeat the command and replace the "Left" with "Right".