Debian has a system of alternatives for various commands (or functionalities). For example, the editor command could be nano or nvi, or one of a large number of alternative editors. You can update the default for this command with:

$ wajig updatealts editor (update-alternatives --config editor)

Another common alternative is x-window-manager. You can get a list of all alternatives with:

$ wajig listalts (ls /etc/alternatives/)

The information is maintained in the directory /etc/alternatives/.