Kanban WIP for Trello v1.0.4resigned1
A work-in-progress limit can be added to a Trello list by adding the limit to the list title in braces. If you name your list "QA [5]", this sets a work-in-progress limit of 5 items to the QA list. When the number of cards in the QA list exceeds 5, the list will be highlighted in red.