Select cards with a common theme by clicking the tick in the top right corner of each card. Then choose Tag from the menu at the top of the page.

You’ll then be asked to choose a short name for the tag.  After you’ve created your first tag, the next time you tag cards you’ll see a list of recently used tags. This makes it simple to add cards to any existing tags you’ve already created.

Another place to add a tag is on the back of the card – just select + Add a tag under Connections.

Click on a tag on the back of card or in the Recent tags section on the All boxes page for a view of all cards that have been given that particular tags. Cards on this page can be copied to other stacks and untagged.