important or already read option
Its not always possible to remember which paper I had read in a pool of 100's of paper. I find that there is no option to mark already read paper or mark the paper for future read. Please add option to mark important paper or already read option in the zotero.
https://forums.zotero.org/discussion/97054/is-there-a-way-to-colour-code-or-otherwise-mark-read-unread-papers
Most people do this with tags. Either manually applied, or with the zotero-tag addon below which assigns /unread and /read tags automatically.
https://github.com/windingwind/zotero-tag
You can create your own 'important' tag with an assigned colour or emoji, so that tagged items will appear marked that way in the main library pane. zotero-tag has some extra options for that too.