As a developer
I'd like to put my pending tasks (waiting for some blocker tasks) visually to some other place than the normal task which can be dealt with without delay. IMHO that visual distinction could be an other swim lane above the normal columns. It would be fully visible only when there are some pending tasks, if empty there would be some narrow bar or sg.
So pending tasks wont get unnecessary attention and the folks assigned to the tasks blocking the pending tasks would be aware of the urgency of their work.
Also this has much to do with the concept of blocker tasks and subtasks. Any visual distinction of these would be helpful (blockers and blocked id-s revealed on cards, and parent-sub relationships)