I have a process for problem tickets.
Problem stores the date of the oldest linked ticket created date in a field.
When you link a new incident, it checks the created date of that ticket, against the stored date. If the newly linked ticket is "older", then that stored date is replaced by the date in the newly linked ticket. I then have automations that do calculations after that.
What I am stuck on, is if you de-link a ticket, then check the linked tickets for the now "oldest" date and set that as the stored field in the Problem ticket.