(No, you didn't miss Part 4 - I just did some renumbering so the articles would list in the correct order by default.)
When I started refactoring the UI code for the original many-to-many checkboxes class I had a pretty clear idea of where I wanted to go.
...
- Checkboxes in a simple queue
- Checkboxes in a file loaded ABC browse
- Checkboxes in a page loaded ABC browse
- Storing results in a database
- Storing results in non-database form (e.g. XML)