Borges' modules are plain text XML files, so any text editor (Emacs, Vi, you-name-it) should be OK. Emacs is the favorite editor of Borges' authors, mainly because its PSGML module makes working with XML files really easy.
Nothing prevents you from using a GUI-based graphical editor, provided that it does not interfere with Borges' requirements and management features.
However, a “pure” text editor is highly recommended because it offers the ultimate flexibility when working with XML files.