None. Site builders are crutches for people who don't want to write their own HTML; you cannot merge site builder content with custom HTML, let alone use them to edit your documents.
One reason is that those site builders use HTML templates, while the content is inserted from a database. Your HTML documents are built in a fundamentally different way.
If you want to use a CMS to manage content but use your own layout & design, I suggest learning how to create Wordpress themes.
Almost any hosting provider out there. That's a very basic feature.
