You cant have on groups tab. But you can create a custom report/dashboard with the fields you want to expose. Tableau server has a repository where all the metadata gets stored. It's a postgresql. Enable readonly user and create the custom report. You can refer to the below video.
Tables information can be found at Workgroups Database - Tableau
Hope it helped.
Blogging at asklaksmhi.com
It is not possible to customize most of the Tableau Server interface "out of the box" It is possible if you do it yourself if you want to play with the back-end code but you will be unsupported and it WILL break when you upgrade to 2018/2019, making it really not worth it.
For getting the back-end db info, heck yeah you can Matt Coles did a great job here: Shareable Data Sources for Tableau Server
And as Lakshmi mentioned, you can look in the Server admin documentation for the data dictionary of what's available.