Hi
I think you haven’t seen that because it’s quite technical and complicated. Anything connected to Collections will not be exported in regular export of the site. The Collection items can be exported as CSV file. And there is not a simple way as I know of to make that CSV into static HTML and CSS. There a some CSV to HTML converters out there but you need to add CSS to that.
My tips to you (depending of how many collection items you have and the complexity of CMS items) is to make the site static inside of Webflow and export it. My other tips is to use a tool from Udesly that can convert your Collection based Webflow site to a Wordpress Theme, not static though obviously.
Maybe someone with good developing skills will comment too help you out.