I have modified a template in Libre Base, after generating a report and editing it.
However, I can not see a way to either re-use a custom template in the report wizard, nor can I see a way after editing the report to change the template to the one I saved…
What is odd is, in the File → Template there is a Save option, but no Open. There is Edit, but that opens the template (stored in the appdata folder) for editing, not changing the template of the report.
Ideally, it would be best to have the Wizard call the custom templates also. Otherwise every single report needs to have the template edited… this makes Base almost useless (because otherwise you might as well use Calc).