Category pane contains the list of categories. The list of categories is unsorted. It seems categories are listed in order they were added. In case of large file with lot of categories it is not convenient — it is too hard to find a category in the unsorted list.

I propose to sort the category list alphabetically.

Alternatively, sorting may be turned and off by clicking on category column header. It is a quite standard behaviour in many programs. For example, look at the list of Ignuit bugs at the project page in Savannah (Bugs -> Browse): by clicking on column header you can sort list of bugs by Summary, Status or ID (in both ascending and descending orders).