Yes, I do mean a 'text box' field. Every time you add a particular value in that field, it saves it. You then get a drop-down arrow next time you go to that field and get the chance to select a value you entered before.

As for the 'pane' question, I mean whre you get the 'tree' pane on the left, and another pane on the right. This might be a single album record, all the albums for a folder (artist) listed cross-tab, or all the tracks for a folder (artist) listed cross-tab.
When you clcik on an artist's folder, and you've selected the 'album view' icon (from the toolbar at the top), you get a cross-tabbed list on the right pane. If you right-click the 'headings' row at the top, you'll get the option to insert a field. Select your custom field from the option list that appears, and it shows on the list.

You can save any particular arrangement of fields in that view by going to the 'preset' box on the toolbar and selecting your choice of action. Depending on whether you have selected 'tracks' view from the toolbar, or 'albums' view, you can save different arrangements. Play around with it and see!
The lists under database prefs are limited (I think, if I remember rightly) by Andre - don't think we can change them. So I don't mean THOSE lists!

Hope this makes sense - had to do it in a hurry. Work gets in the way!!