How are you generating your new draft from your template?
This approach?
i.e. Utilising this action?
If so, you should be able to get just the body rather than the full content of the note being used for the template by modifying the action and changing:
d.content = d.processTemplate(template.content);
to be
let astrLines = draft.lines;
astrLines.shift();
d.content = d.processTemplate(astrLines.join("\n"));
There are other ways to do this, but I think this might be a reliable and easy to understand one … RegEx might lead to too much complexity to cater for escaping title content and erroneous single line templates.