I wasn't thinking of the UI being "highlight text -> context menu -> translate", rather, one of:

1. Open bonjour.md and a banner automatically appears above the document asking whether you'd like to translate from French -> German (assuming the desktop environment language was set to German). This is more or less how Firefox handles offline translation of web pages.

2. Open bonjour.md and click a translate button, then get asked which language pair to choose from.

I can however see how the "highlight text -> context menu -> translate" UI pattern may make sense in multi-language settings, such as a chat room, or web browser where text in multiple language may be presented on the same page. For a terminal session however, it may be better to require the user to pipe text to a translation command line utility where possible--but there are exceptions to this too such as ncurses interfaces.