Select any number of incidents and click on reassign on the header of the incidents table.
You can reassign an incident to a team member. Not all incidents will have assignee to it, especially when you have Slack app notifying you on channels.
Once reassigned, the user will get an email notifying them about it.
Your escalation policy for the incident will NOT be affected. It will continue as is.
You will see the reassign incident option on every incident table. More particularly it can be found on -
Incident details page
Incidents listed for a service