This is a Qt-based GUI tool designed to create and edit .torrent files.
Some of its features:

  - Create .torrent file from scratch
  - Edit .torrent file in user-friendly way
  - Edit .torrent file in JSON format
  - Add, remove, and interchange files in .torrent file
  - Support for different encodings

WWW: https://sourceforge.net/projects/torrent-file-editor/