Engineering Report - How can I store my report templates ?

Although the Engineering Report is a separate process, the report(s) themselves are included with the project and packed in the esa-file.
You can store the layout and formatting of a report by saving the project and using it as a template-project.
This template project can contain multiple report types, each dedicated for a particular case.
The content of a report strongly depends on the type of the project (1D, 2D, steel, concrete, linear, non-linear...). 
Therefor it's logic to consider project and associated reports to be part of a template