Customizable invoice

I know, there is a way to make custom field in invoice template. But I can’t find any options for call this new field in the html code of invoice. (eg.: "data-bind=“text: Number”).

I’ve read several comments, and there are a lot of different rules by the countries what must be on the invoice.

Otherwise, I think it would be great, if we can make lists (eg. invoice list or tax transaction list in the Manager) with this new field.

Thank you if you going to spend your time for this.