Storing List of custom type in Win Forms application settings

Question

I am trying to store a List of a custom type in application settings and have been unable to get the collection editor working properly. My class appears in the settings Type dropdown, but when I go to enter a value, there is an arrow that opens a box to edit the plain text value instead of "..." to open the Collection editor. I did the same thing as this person, but either something changed since the version of Visual Studio he used, or I did something slightly different.