You should never have more than H1 tag on a page, so creating a list of "H1's" would be bad practice and terrible for your SEO.
You can't add <h> items or <p> items into the Bootstrap Studio List Component.
If you want to have headings or paragraphs in a list, you'll have to use the custom code component and write it by hand (though I honestly can't imagine why someone would want to do this. Headings and paragraphs have specific semantic meanings which are both different from that of a list.)
Interesting work-around, but I still can't understand why someone would want to put headings inside a list. I can see using a heading before a list, to describe what the list contains, but inside a list makes no sense to me.