There isn't any rule, the team decides on how they work and how to signal different things occurring.
As you mentioned, you can add dots on the issue for each day it stays on the board, you can use different colors for the issues you will want to pay more attention to, if you have a physical board you can you can tilt the card from this ■ to this ◆, and the most obvious choice is to just place the issues one on top of each other and the team works on and picks from the top (just like a backlog is ordered for example, and you pick from the top), etc.
Kanban says that you should limit work in progress, so if an issue is long lived in your board, that's a sign that something must be happening (maybe something is blocked or waiting, maybe a team member is having a hard time and others in the team aren't helping, sometimes it's a sign that people are loaded at full capacity each with their own tasks and everyone minds their own business instead of swarming to relieve pressure points, etc). Your team should find a way to solve it and clear it from the board to limit WIP and thus improve flow and increase throughput and value creation.