Hello links, so far I can only suggest to print your list to PDF format - thus the numbering should remain. Both Mac and Windows 10 allow to print to PDF without extra software installation.

Possibly this could help in your scenario.

I am writing my doctoral thesis and landed on checkvist while searching for a numbered outline option where I could fill in my outline without worrying about formatting. Scrivener/ Microsoft word and other softwares do not give this easy visualisation that checkvist offers. Yet when I export the final outline, I get just a list of words that looks like a grocery list. I almost purchased the pro version since I was immensely motivated to write more when I saw the numbered and indented outline emerging so beautifully. I have been wasting an hour now to try and convert the outline to the same format in word and its too much of pain really. This is a let down actually, considering there is no other app like checkvist, in terms of keyboard shortcuts, and other minute thoughtful additions. I even loved the fact that you can add a few lines by hitting shift+enter. This way I can fill in a few lines of abstract for each sub-section too.
Please allow the numbered-list to get exported as-is.

But we have many export options, to text, HTML, OPML etc.
In this case, we should include numbers to other types of export too, right?

So far, the numbering is visualization only option, and we use browser features to implement it.

Numbering implementation for export is not very complex, but it would take noticeable time and I'd collect some more votes before implementing it.