(Backbone) Where is the Backbutton for the Survey defined?

[Thormgrim]

Hello, 

I'm currently reskinning ResearchStack for my app and now have been able to get ResearchStack working in a different Frame as well as moving stepcounter and the like.

The only Element I cannot find is the Backbutton for the Survey / Steps.

Can someone direct me to the correct file, where the Survey Backbutton is defined?

Any advice and help would be greatly appreciated.