I’m sorry my fault. On searching for a good screen for customizing the results, I switched to customize the Push-Defect Dialog… So forget the former advice, you are one steps before this.
Then I thought to check for adding your template as a pre-content for the comment field. But I wasn’t able to find it in the docs somewhere - and I don’t have access to a system right now. Probably it is possible, but I can’t give you the right tip. Sorry.
But two remarks to your process at all.
You can easily add your additional information as simple fields in the result itself. Or even all other fields as well.
Your result looks more like a defect description and not a result following a defined test case. Do you start with a real description or more or less in a free test session? Probably it is easier to create cases with steps on the fly and create a result afterwards. This makes it easier to give structure in TestRail.
So sorry again, but maybe it helps.