The problem I have is that when I want to include the Description field in the Navigator list it generally makes the screen have a horizontal scrollbar in addition to the vertical one that is displayed with a list of much size.

So what seems like a nice solution to me (or at least one I've seen before) is that for long fields like the description or the summary maybe allow them to be in a separate row under the other fields where both fields are still lined up with the main id. So basically the key field would span multiple rows and the description field would span multiple columns in its row.

This is probably similar to JRA-4629 but I created a new issue since it seems to be a little bit different. There may be some other methods to try and keep the horitzontal scroll bar away like allowing the left column with the filter data to be completely hidden and brought back if necessary to change the search.