Annotation of a ==single line [[works fine]] currently==
I’m using the highlight as annotation more than as a markdown style.
Highlighting across line would be great.
=1=Pairing/labeling/coloring =2=even=1= better=2=
Generally I’d like to mark many spans,
possibly overlapping,
possibly invisible,
as little syntax debris as possible.
I agree that highlights is so limited for detailed annotation. But on other hand adding such to base markdown is against the minimalistic nature of it imo.
Is HTML is better than markdown in this regard? If so the only problem for conveniently using it is adding a plugin for GUI as html tags are already supported here.
Also I don’t understand why the markdown formatting assistance plugin doesn’t even support simple highlighting.
What would a block of text look like with html tagged spans?
I have not tried extensive highlighting in markdown yet, Its just an idea, maybe you can test it and tell us. I don’t even know which tags are for highlighting in html. I currently trying to figure out the best use of highlights in pdf, as it already has a standard format to work with it
Superb idea! 
So highlights would be even more useful to consolidate knowledge
Colors in Obsidian are bit overlooked right now…
Highlights and colors tell us immediately meaningful information, like
Folder category
Colored folders by @Lithou
Citation
Admonition (plugin) by @valentine.195 Notation color box (rss) by @death.au
Also, a context menu with multiple color choices to highlight selected text would be awesome… One configurable highlight is nice, but a little bit limiting