Not sure if I know where you want to create that. There already is a dashboard that is intended for that purpose that you can read more about here

https://webhelp.episerver.com/latest/en/platform/dashboard.htm

Some examples to create some custom things using iframes for that dashboard

https://devblog.gosso.se/2017/06/convert-deprecated-gadgets-to-components-in-episerver/

Other parts of the menu is also extendible if you want it somewhere else. You can extend the navigation with new tabs

https://world.episerver.com/documentation/developer-guides/CMS/user-interface/extending-the-navigation/

An example is the audit tool 

https://blog.nicolaayan.com/2018/05/growing-episerver-dxc-instance-you-might-want-a-tool-like-this/

And you can find example code here

https://github.com/nicolaayan/EpiserverCmsAudit

Hope that helps getting started to extend Episerver with some custom dashboards