Well, I finally found how to add a button to the "Compose" window, but not yet to the main bar.
When clicked, it opens a ... "pane" (is that correct"?), where I guess that I will be able to display my form & get input. I would have preferred to totally replace the Compose window with my form, but it doesn't look possible(?).
Right now, I am trying to discover how to debug my JS. Thanks for your feedback
If that wll wor across all platforms, then it seems the best approach. It is my beliefe that 99%+ of my users will only use desktop, but, still ...
I am certain that your presentation and github project are going to be of tremendous help.
Btw, do you know if there is a good book available about developing Outlook Web Add-ins? I find lots of contradictory info on the web, some of it probably out of date & am looking for a canonical referecne source.