I'm trying to disable the new share button on the top right corner of the Office 2016 apps.
Does anyone know the correspondent IdMso? I've tried to locate the IdMso tables but I only find tables for the previous versions of Office.
Microsoft has published the IDs for Office 2016 here:
Office 2016 Help Files: Office Fluent User Interface Control Identifiers
As far as I can see, however, the Share button at the top left is not part of the Ribbon, i.e. you cannot remove it using a custom Ribbon XML (you can easily check this by providing a Ribbon XML which resets everything).
In case that you don't know the ID of a control, there is also a simple way to retrieve it inside Office: Go to File > Options > Customize Ribbon and hover over the respective command or group:
Command:
Group: