+ Tap the Settings tab
+ Start the REPL (top right button)
+ Tap the REPL help (top right button)
+ On the first line of the help is a link to show library.org
The library.org available above does include some documentation (although could be improved) to give you an idea of what can be changed.
You can set the tab to open by default. If you haven't used the beorg init.org before see https://beorg.app/learning/excluding-tasks-from-specific-files-for-the-agenda-and-todo-lists/. Then in your init.org add (substitute todo for files if wanted):
(set! ui-start-tab "todo")