The WorkshopManager allows you to create, update, and manage your Custom Game workshop items.
This will bring up the workshop manager, which will populate your list of published addons when it starts.
Creating or Updating an addon
The first two icons in the Workshop Manager allow you to create a new addon or edit an existing addon respectively.
Publishing an addon
Creating or editing an addon will bring up the addon publishing dialog. When editing an existing addon, the fields will be filled in for you.