Chromebook Tricks for Teachers - Best Bookmark Bar Trick
To add bookmarks as just a small icon in your bookmark bar, do the following:
Add a bookmark by pressing the star in the top right hand corner of your omnibox (where you’d type a URL into Chrome).
Where it says “Name,” delete all of the text.
Check to make sure “Folder” is listed as “Bookmark Bar.”
Press “Done.”
If you’re a more visual person, this video will walk you through exactly how to make your bookmark show up as a small picture.