Please help us help you and fill where relevant:
Your LimeSurvey version: 3.28.x
Own server or LimeSurvey hosting: self hosted
Survey theme/template: custom
==================
Hey experts, do we have any kind of documentation for the LSS XML syntax and file structure?
Do you know of any XML tools which could analyze and visualize such an XML structure?

Thing is that we want to try building a survey with external tools and then want to generate the required XML structure to import that survey.