NewUX : Hide Boards / Sheets

Similar to how the Contents area works in Classic to have the same ability to do something similar within New UX.

Want to be able to have a main board and then users go off to collect more information, but that they can't go there directly as it doesn't make any sense to do so. This links nicely to the following idea about having additional insights available on boards (https://community.anaplan.com/t5/Idea-Exchange/New-UX-Make-features-in-Board-and-Worksheet-page-layouts/idi-p/61974).