Hey @James!
We had a word with tech team and they let us know that If you create a template with some parameter, it is required to fill them all otherwise the API will throw an error "Number of parameters does not match the expected number of params"
Also for new-line/tab Character concern you should include them in your template and approved the template from their team then only you will be able to work with new-line/tab.
For further information you can contact the Facebook support team.
We had a word with tech team and they let us know that If you create a template with some parameter, it is required to fill them all otherwise the API will throw an error "Number of parameters does not match the expected number of params"
Also for new-line/tab Character concern you should include them in your template and approved the template from their team then only you will be able to work with new-line/tab.
For further information you can contact the Facebook support team.