I am looking to replace the Word ActiveX we are using in our web app by CODE. Is there a way in CODE to select and replace text and to manage bookmarks and comments programmatically?
There are indeed ways to use macros online.
See this announcement Major new features with macros and Draw in Collabora Online update - Collabora Office and Collabora Online
and this extra blog How to use and manage Basic and VBA compatible macros in Collabora Online - Collabora Office and Collabora Online