This feature is now on the backlog. I will update you when we have more details to share.
Thank you for your feedback! We support adding multiple pages to a single Wiki tab by choosing the “Create a new page” button on the bottom of the Table of Contents pane. This pane can be opened by tapping the menu button on the top-left of the Wiki.
We’re working to make the Table of Contents easily accessible on larger displays so that this option will be just a single tap away!