Here is a link to the
Help files.
There isn't any way of adding buttons to the Tool bar in this version of Audition. Also there isn't a Favorites Palette as such. You can Record new Favorite scripts from the Favorites menu. Also if you have set up an Effect you want to add to favorites just click on the Star icon to the right of the Presets box. This will then be added to the Favorites menu.
You can have something similar to a Favorites Palette by adding Effects to the Effects Rack, which you can either dock onto your Workspace somewhere or have it undocked and floating.