It is not clear what you need. Escalations on SLA's are so complex. There are several activity steps OOB in Pega for handling them ... like "Notify Assignee", "Notify Manager", "Transfer", etc.  I would start with this L-1621 lesson in the SAE II course from Pega Academy.

Chapter 7 : Enforcing Business Policies

        Enforcing Business Policies Using Service Levels

For instance, from this material - "In addition to changing the urgency value, we can also define an action to take to escalate the assignment if any of the milestones are missed. Common escalation actions might include: Sending notifications to the assignment owner and or their manager; we could transfer the assignment to another user; or maybe even kick off an “escalation flow”".

The complexity from there grows very fast.

For example, a lot of customers create sub-cases during their escalation process which may involve a new work pool or work party while maintaining reference to the originator (case, pool, party, access group, etc.).