Lumi Favourites is a way to highlight your go-to cards, Boards, Kanbans, Schedules, media or whatever you'd like to bookmark.
Your favourites bar can be found by pressing the star in the left hand column of your browser window. 
To add something to your favourites:
Step 1: Open the item.
Step 2: Press the gold star in the top right corner
The star will go from an outline to solid gold
and now that item can be found in your favourites list.