DTTG: pasting html content in formatted notes

Hello! I’m trying to get comfortable with DT & DTTG, including rich text editing. I miss some of widespread features like horizontal lines, checkboxes etc. I saw questions and answers about some types of rich content, e.g. on inserting horizontal line, pasting checkboxes and so on. I’m not asking for implementation in the app, just trying to do it myself.
XCode > New iOS app. Ok, here’s is the simplest Swift button code to copy a horizontal line into pasteboard:

if let hrData = "<meta charset=\"UTF-8\"><hr>".data(using: .utf8) {
	UIPasteboard.general.setData(hrData, forPasteboardType: kUTTypeHTML as String)	

I can paste line into editor view but DTTG doesn’t preserve it after foramtted note is closed. The same happens when I copy horizontal line from Safari or any other app. Desktop version however does support horizontal line saving. Do I miss something or is copying and pasting of such web content prohibited/ignored on DTTG? Or maybe the’s a correct format that can solve the case. For instance I see content copied from DDTG’s formatted note has data for Apple Web Archive pasteboard type. Shall I compose one? Any suggestions?

There seems to be no provision for editing formatted notes, although you can paste into it (seems a bit weird to me).

If you really want to edit HTML (which is the underlying format), you probably need a different app for that.
Alternatively, you could use markdown and CSS (which I’d advise) because it is a lot easier to type and maintain then HTML. And you can use HTML directly in MD, too

I don’t. I made a simplest app that copies a horizontal line into pastebord. And it can be pasted into a formatted note, but not being saved. Only desktop version saves formatted notes with horizontal lines properly.