Today, Microsoft released the December update of OneNote for Windows 10 to Windows Insiders, adding a couple of new features. Right now, it should only be available to those on the Fast ring, although it should make its way through the rings pretty quickly.
The most notable new feature is the digital ruler. This can be used to help you to draw a straight line when inking, and it can also be used to measure distance. As with the ruler in Ink Workspace, you can rotate it to a specific angle and such.
There are also improvements to the app's search functionality. It should now be faster, with search results now appearing "instantaneously, making it easier to get back to your notes."
That's all that's new for the month of December. If you're not a Windows Insider, you'll likely see this update within a couple of weeks, before the team heads off for Christmas vacation.