Hi Matthias.
take some simple device view (XML) from GitHub and open it with your favorite text editor.
Example: DeviceViewCiscoVlans.xml
reportId = unique identifier without spaces
title = not sure if unique but why not have it unique...
viewTabTitle = the visible tab name
viewOrder = if you have more tabs then the lower number is more left
family = what family you want this tab to show
viewId = name of the flexview
Once you are happy with your edits, follow the procedure of installing your own device view. procedure is at GitHub also.
When you have simple device view working, take some more advanced and I am sure you will understand it quickly. Example: DeviceViewCiscoResources.xml
Once you are happy with the result, feel free to share it with community.
Enjoy weekend!
Z.
Regards
ZdenÄk Pala