In short, no. That would be a whole different paradigm. The display features of the map were generally added to offer ways to help indicate meaning, rather than as a form of WYSIWYG word processor.
The preview arose as an (HTML) export preview, how your note looks in a web browser when your note is exported. A sub-set of users have since taken to using it to see text in styled form either because they like writing in Markdown and viewing a rendered version, or the RTF set of tools are not to their liking. But, by original design and intent Preview is still an HTML export preview (some may be unaware mmd is just a different form of inline HTML mark-up that has to be post-processed into HTML to make the ‘visual’ form).
As I recall one of the big drivers for a fully RTF $Text area was that a sub-set of users really wanted highlighting of text as it is central to how they conceive annotation. I note the latter to make the point Tinderbox is a tool for notes and note taking and sense making, not a visual design space. In that context is there a need, other than visual aesthetics, behind this question? I ask because if there is and we know it there might be a way to achieve a similar effect without needing to try and do everything via export markup.
Taken with your question on text layout it appears that you are approaching your note-taking working back from an imagined visual ‘look’. There is nothing wrong with that but such an approach makes it hard work as Tinderbox is not a web page design tool. The core part of the tool is the note making and analysis thereof. If you know HTML & CSS then you can likely export the pages you imagine, but if not you can still export more basic pages and give them to you web designer to finish the style.
HTH 