Hi Stephan,
In Sensible TableView, all you need to flatten out the UI in sections instead of cells with detail views is simply create these sections. For the taskSteps example you mentioned, you would remove the taskSteps property from the Task class definition, then create an SCArrayOfObjectsSection bound to these taskSteps.
Also, for the case when you're having several of these sections that need add buttons, we are now studying to have the add button get automatically generated as an extra cell for each of these sections (will only appear in edit mode). We will try our best to have this part of our next release.