Enterprise Architect enables you to change the order of elements listed in the Project Browser window.
Elements by default are first listed in order of type, then of set position, then alphabetically. You can use the context menu options to move an element up or down within its type, but not outside its type. This means you can resequence Packages or Diagrams or Use Cases, but you cannot mix elements up.
Ordering elements is very important when it comes to structuring your model, especially packages. RTF documents honor any custom ordering when printing documentation.