We're using Macrobutton type Word Fields in the VSTO add-in that is already developed for Word desktop. We're in the process of extending our feature to Word web version and we happy to have Macrobutton fields in Office.js API also. In terms of our feature, we need to insert and tag the content with Macrobutton fields in Office 365 Word web version and also need to open up a document which tagged using desktop addin and edit the tagged document using the web version.