Let suppose that we have two tasks with equal priority (let's say both are set to High priority in Jira). But the work on one task was started a couple of weeks ago, and the work on the other task was started a few days ago. The first task is just going hard, maybe because of being blocked for some time or maybe because it's been returned back to development after testing, it doesn't matter.
As far as I'm aware, in Kanban we treat the older task as more important (both are set to High priority, but the older one has a relatively higher priority) because we strive to make our service fast. So how do we maintain this relative priorities (make them in visible, noticable on the board), so that the team always knows the relative priorities and tries to complete the older tasks first?
For example, in Jira there are dots on the issue showing how much time the issue has been in the column, but these dots get reset if we move the issue on the board forth and then back, which makes these dots not usable for tracking the time the issue has been worked on.