Check if the linked issue is in specific status, before transit the status of "main" issue

[Lukas]

Hi folks! Is it possible to hold the transition of an issue, until the linked issue reaches a specific status like "DONE"? I did similarly before for sub-tasks with the help of some experts from Atlassian community, but I'm not sure, how should it work for linked issues. Here is the screenshot, what I mean: So the requirement is, when the linked issue (is mitigated by) is not in status "DONE", you shouldn't be able to transit the "main" issue to the status "MITIGATED". For sub-tasks I've used Flag, but for linked issues I'm not sure, how the automation rules should look like.

[Jason Waller]

You can achieve this using validators in your workflow transitions 

[Lukas]

Can you explain it with examples, what do you mean? The thing what I want to achieve is just, until I change the status of linked issue to "DONE", should the "main" issue not be able to go the status "MITIGATED".