Hi Marvin,
The basic: Siberian is an app generator. User can add or remove page/feature/module/layout without needing to republish the app. It means, all modules and layout available on CMS is automatically loaded into app as well.
To modify (which is not recommended), user need to understand Siberian Structure. To alter the code, user need to understand Js, php/phtml, etc..
Now, if you want to modify app permission, you also need to remove all related features in the app source code structure.
I have done once but app failed to open and so I stop trying. There are some other methods I have done but now decided to follow Siberian rules :)
Please feel free to email contact@siberiancms.com if my opinion doesn’t satisfy you ;)
Sincerely,
Ariv Ontowiryo