Add accessible filters

[JumanaFM]

provide other accessible filters in addition to what we currently have. We know from previous data that users don't use bookmark so maybe use another filter instead such as "from following list, instructor endorsed"

[semisenioritis]

Maybe have a system where highlighting the text on the document, shows up threads in the top of the sidebar, which have the same or common highlighted text as the root text from the document.

This way, rather than having scattered discussions with everyone asking duplicate questions, students can get redirected to threads concerning this specific "highlight" and can go through the threads before making a post.

Especially useful for focus mode when you don't want the distraction/overwhelming number of annotations but at the same time are stuck at a specific place. The readers can be encouraged to maintain their own mental flow without excessive annotations and at the same time get specific directed help.