Hi Susan,
I could find documentation for creating custom pages for the desktop version, but not for mobile.
Although in practice you follow pretty much the same process for desktop and mobile, the option to select a custom mobile page doesn't appear in Community Admin until after you've created the custom mobile page. This might not seem like an issue, but when combined with the omission of mobile pages in the documentation, it makes it look like you can't create a custom page for the mobile version of a specific node. In fact, I only realised you could when I found a forum post that implied it, and decided to experiment.
This could be solved with two simple changes:
1. Show the drop down list for selecting a mobile custom page even if no custom page has been created yet (can be read only if no valid options).
2. Update the documentation to explain how custom pages work on mobile.
While we're on the subject, the process for creating custom pages is probably unecessarily obscure - instead of having to follow a special naming convention, it would be much more intuitive to simply have an option when creating a page to specify which in-built page you wish to customise.
Thanks