Scenario: On your website, you are featuring content on the homepage that has a full write-up in an inner page. You'd like to "tag" the homepage content by creating an association item that lets your clients select which inside page the Homepage should link to. However, the homepage might link to a number of different types of content inside your website.
The Problem used to be: Associations could only be associated with a single collection, so it was necessary to create multiple associations -- one for each potential type of content. This was not an ideal solution.
Solution: Associations can now include as many collections as you would like. Simply select the additional collections from the dropdown menu and build an association that fits your exact needs.
This will be especially powerful when we release our new Permalinking features next week that will allow you to completely control how each Structure is Permalinked.