First, so sorry, I meant to refer to Google Docs not Google Sheets. Templates on Google are created in the Docs app and you can insert tables to control formatting. It may be its not needed in your case but I have feeling it might before you are done.
I don’t think you can list multiple
<<START>> blocks like you have done in your Excel template. It’s likely possible you can combine them into a single one and use
<<IF>> conditions to report values.
At any rate, if you are not locked into using Excel as a template, I would strongly recommend to spend some time familiarizing yourself with creating templates in Google Docs and using those in your automation. It will give you more value in your app in the long run.
I am not sure what “boot” is referring to here. Could you mean Bot? I’ve never relied on automatically generated templates so I’m a little unfamiliar with the process.
As for your reference to (XLS), I assume you are referring to the HTTP Content type setting of the generated document (see image below with XLSX set). This is the content type of the FINAL document - not the template itself. The template can be created either with Google Doc or Excel but Excel is not as flexible.
In Google Docs you can do something like in the sample template below. You cannot create the same in an Excel template. Note that a
<<START>> block is inside of another
<<START>> block allowing me to report on each Ordered Kit and under each Kit item from the first START list show a table of the Products ordered in that Kit - another START list.