I’m currently writing my thesis and the number of times the need to do this has come up is enough that I am replying to this 
Here, as I was writing, I realized that “hippocampus” notes might be relevant to this.
I scanned through the backlinks for “hippocampus”, and found a specific line I had written in a note for one of the papers in that list of backlinks. You can see I try to select that specific chunk of text, but as you point out, that only lets me insert a link to the paper’s note.
Rather than being able to select and copy that text directly, I had to open that note, scan through to find that sentence, and then copy+paste it to my original note.
Whew! I’m surprised I didn’t forget what I was trying to do in the first place!
It’s frustrating because the text is riiight there, yet there are so many steps that I need to take to get that into my working note!
EDIT: Writing this reminded me of this very eloquent comment in another feature request, re: taxing working memory, ADHD.