You can add Cards in bulk to a List from a search in your Project Library. 

Hit the bookcase icon on the far left of your screen to access the Project Library. 


Select "Cards" and filter your search by card category, fields, or type a keyword.

When you have all the cards you wish to add, select onethen hit the double ticks that appear in the bulk actions toolbar to select all.

Choose the "Add to List" option and select your List from the dropdown menu and "Add Selection".