You might, for example, read a paper in Mendeley about the taphonomy of mammal carcasses. There's an interesting line about teeth: that while they are more resistant to weathering than bones, they can still crack and split in hot and dry environments. You highlight this sentence and add an annotation with your thoughts.
But how do you find that annotation at a later date? Until you read that paper again, you might not remember that it even exists.
Mendeley does not allow you to view all annotations you've ever created, or even indicate which PDFs either do or don't have annotations. If you remember reading something interesting and writing something about it, you better hope that you remember what you wrote, as you can find annotations by searching for key words within them. And if you're like me and just want to review your past notes, good luck trying to remember all the papers you've added annotations to over the last 6 months.
You could copy the contents of each annotation in to an Excel spreadsheet or mind map, and group them by theme. That way you can review your database or mindmap and find your way back to the original paper. But this feels like double handling - why not just write the annotation in the mind map in the first place? What I would LOVE is a mind-mapping tool within Mendeley, where you could click and drag annotations on to nodes/branches, but I realise this could be nightmarish to code and implement.
I can't say I've come up with a solid solution for this problem yet. Has anyone else figured out a better annotation workflow for Mendeley, or do you use other software and reference manager combinations to keep track of your research notes?