This is useful for adding greater numbers of resources quickly (without having to verify each one). Be mindful to turn OFF Quick Add once you have finished (otherwise any resource clicked will be added to your list).
1) Navigate to List Builder and select the list you want to add resources to.
2) Enable the 
to resize option.
3) Begin searching and clicking on the resources you wish to add to your list. Any item you click on will be added directly to your active list.
4) To stop List Builder from adding resources directly, disable the option.