Why can't I add a new template on my ecommerce site?

I recently took over a Shopify site. I think they might have a custom site with restrictions on adding pages? I can’t add a new template. The drop down doesn’t give the option. Is there a way around this?

Website: https://www.beigestyle.com/

TIA

@jmiles

You also create the page template from the code editor.

online store >> edit code >> template >> add new template

after that select template type from the dropdown and choose the type of template json/liquid.