Here are the multiple Customization options for Threshold.
* Add Games Button re-adds the "Add Games" button 
* Collapsed Sidebar shrinks the left-hand sidebar
* No Downloads Button removes the button for Downloads and brings back the "Downloads Completed" text
* Switch Bottom Bar switches the Account info and Notifications with the Downloads section
* _Default is the standard configuration

There are also folders for combinations of options, where appropriate

Other options are located in _Misc. See the seperate README for more info

To install, copy the contents of the appropriate folder to the root of the skin (where config.ini is). Confirm you want to replace files, then restart steam.