How to change the home dock icons on TouchWiz?

Similar to https://android.stackexchange.com/questions/27411/how-to-edit-the-home-dock-icons-shortcuts-on-touchwiz-4-0-ics I have a Samsung Galaxy S3 GT-I9300 with Android 4.0.4. I can't for the life of me figure out how to edit the home screen dock icons on the default launcher (Touchwiz). I've tried: - Long pressing on a home dock icon (nothing happens). - Long pressing an app in the home screen to drag onto the home dock. (Home dock icons disappear and are replaced by a Delete bar across the bottom of the screen) - On the home screen, press Menu -> Edit. (Home dock icons disappear and are replaced by 4 icons: Create folder, Create page, App info, Delete). - In the Apps list with a Customizable grid view, press Menu -> Edit. This is the answer to the linked question. (Allows editing of the Apps listing, but doesn't bring the home dock icons onto the screen so I cannot modify them) Before I updated to 4.0.4 I could change the shortcuts in the home screen dock, and I put Google Chrome there to replace the default browser. After updating I now want to replace it with Firefox. I am in Australia. I have friends with grey imports of the same phone from Hong Kong that don't exhibit this behaviour on 4.0.4.