I was just reading a note in Obsidian and caught myself thinking, “If only I could underline this passage and draw an arrow pointing to another, just like on paper…”
Sure, I could export the note as a PDF and annotate it there, but that comes with its own drawbacks: losing the ability to edit the note in Obsidian, reduced searchability, and the sheer hassle for something as simple as an underline, an arrow, or a quick doodle. 
Obsidian excels in so many areas, but when it comes to visual note-taking, even good old-fashioned paper has it beat.
I really hope this becomes possible someday. While I don’t expect a core feature, a well-designed plugin for visual annotations would be a godsend!
Some relevant posts: