Is it possible with current version to have line spacing? I tried hacking it with .ace_line { height: … } and .ace_line_group, but the result is not perfect/clean.
Can you explain how line spacing is controlled? Assume some users don't know CSS or html and use Joplin because it's advertised as a notetaking application.
Of course. Just as one could have a photo editing app that would work only in black-and-white. But why would a developer do that? It would kinda limit the market adoption, wouldn't it?
Add this CSS to userstyle.css. It enforces single spaced lines and a fixed line height for HTML elements inside the parentheses. In this case, only paragraphs and lists are affected.
To affect only paragraphs, use #rendered-md p instead. :is() isn't needed since p is the only child element.
I'd treat elements like headings (h1 to h6) and table differently than text. If leaving them alone doesn't suit you: duplicate the above CSS, select elements that need like spacing, and adjust their property values.