Document Viewer for .NET MVC UI Example - how do I enable/disable UI functionality?

Hi, I have cloned GitHub - groupdocs-viewer/GroupDocs.Viewer-for-.NET-MVC: Moved to https://github.com/groupdocs-viewer/GroupDocs.Viewer-for-.NET/tree/master/Demos/MVC and got it running locally. I am trying to work out how to remove some buttons from the view? I cannot work out how to do this. What framework is used for the UI? I am used to working with Razor views, but not familiar with the code in the index.cshtml. I have tried searching for some classes and ids from the DOM but can’t find where this code is. Do I even need to do this or is there a way to pass some options of what functionality is required? There are some keys in the Web.config that look like they should enable/disable some functionality but these do not seem to be having any affect. We are using very old version of group docs; 2.19, so I am attempting to upgrade us, in this version you could control which buttons are displayed.

Thanks, would appreciate any help and steering in right direction. Tara

@Tara.Smile

Please note that GroupDocs.Viewer for .NET 20.x is UI-Independent, back-end API that could be integrated in any (new or existing) .NET project without any third party tool or software dependency.
Have a look at these open-source projects. You can create customized tool-bars or buttons in them.
You may find following resources helpful: