A few months ago I released a visual studio extension, that provides autocomplete if you edit office ribbon files. The extension is open source, and published on GitHub.
By now, it proved to be more of less functional and even some issues with Office 2016 icons were fixed thanks to the user feedback! 🙂
What it can do for you - it can assist you if you edit the XML files to define interface for your extensions in the Visual Studio editor.
The code is based on famous glyphfriend extension (if you don't use it yet - you should start, it's great). Initially there was a plan to merge this part into that extension, but it proved to be quite heavy with all those 5000 office icons, so it is now separate thing.
The extension provides autocomplete for CustomUI for office ribbon (means, auto-complete for the built-in item identifiers, like idMso, insertBeforeMso, insertAfterMso and imageMso).
Extension supports all office applications (i.e. not only Visio, but literally all microsoft office applications) and is enabled by opening ribbon XML file in the Visual Studio editor, which belongs to customUI namespace, i.e. "http://schemas.microsoft.com/office/2009/07/customui"; or previous version.
The extension database relies on the published Microsoft files, and includes the microsoft idMso database and msoImage database. Office 2010, 2013 and 2016 are supported. Reference links (thanks to):
Please see the full list to pick the version suitable for your VS.
The extension adds some settings
Feedback is greatly appreciated (please post suggestions/bugs to GitHub)