I'm trying to create a custom e-Newsletter template duplicating default themes at wp-content\plugins\e-newsletter\email-newsletter-files\templates\
but I'm getting an error and can't find any documentation about how to create a custom template.
There are some old messages saying that doing a template like this could lead to problems (template deletion) when updating the plugin. Other messages says that I must create a custom templates folder, but the requirements are not clear.
How is the right way to duplicate a default template and customize it for e-Newsletter plugin?