OpenDevEd has been streamlining our Google Workspace workflows for many years, going back almost until the initial launch of apps script. For more details about all our Add-ons, see Our Tools.
bTranslate is an add-on for Google Docs. It allows you to replace selected paragraphs with a translation of selected paragraphs while keeping original texts as additional paragraphs or footnotes. You can use translations provided by Google Translate or DeepL. To use DeepL bTranslate will ask you to provide a DeepL authentication key; there is a free tier available.