Hi @sami , result reports templates that come by default with SENAITE can be found here:
However, better create your own add-on instead of modifying the base code. In such case, you can easily add your own reports by creating your own reports folder and register it in a configure.zcml file as an static resources directory:
<plone:static
directory="reports"
type="senaite.impress.reports"
name="MyAddon"/>