Hi @jtm2020hyo
Cut planes are not so often used in Civil 3D, but they do exist. This is a native feature to AutoCAD Architecture, so all the documentation online will be relating to that, but all the same functionality is available in Civil 3D. On your status bar you should see the cut plan icon. Or perhaps go to you status bar customization icon (the hamburger button in the far right) and check mark it to add in the status bar. Once you click it, you can define the elevation range that you want to see, this effectively assigns the global cut plane applied to the entire model space
if you type the command DISPLAYMANAGER you get access to creating custom configurations as well, which architects use to apply to viewports for different levels in a building. I personally assigned different configurations for when designing an bridge overpass.
here are a couple of online documentations Links for additional info:
Link 1 and Link 2
hope this helps,
Samir Rezk
Technical Support Specialist