If you're an Office Insider on the Slow ring on Windows 10 Mobile, you should be seeing a new build that is a preview of the June 2017 feature update. The update was released today and brings the software up to version 17.8269.
While there isn't a whole lot in this update, there is a new feature to PowerPoint that will allow users to "add, change, delete, or reply to a comments in a presentation" from your device. This is a feature that is also present in PowerPoint 2016 and PowerPoint 2013. Excel will also be getting an additional feature that will allow users to open files that contain Dialog sheets.
The update for the Slow ring is similar to what was released yesterday for Android. Android users saw an additional feature that enabled a new numeric keypad.
If you'd like to try either of these new versions, you'll want to sign up to be an Office Insider. These early builds will give you access to new features and will also allow you to provide feedback to the Office team to improve the software using real-world input.