Hi there,
Found this PowerShell script try to execute this and see if this can help you in getting your requirements fulfilled.
$incident = "IR3406"
$username = "Lopez"
$domain = "LAB"
Import-Module SMLets
$i = Get-SCSMObject (Get-SCSMClass System.WorkItem.Incident$) -Filter "Id -eq $incident"
$u = Get-SCSMObject (Get-SCSMClass System.Domain.User$) | ?{$.Domain -eq $domain -and $.Username -eq $username}
$r = Get-SCSMRelationshipClass System.WorkItemAssignedToUser$
Get-SCSMRelationshipObject -Relationship $r | ?{$_.SourceObject -eq $i} | Remove-SCSMRelationshipObject
$n = New-SCSMRelationshipObject -Relationship $r -Source $i -Target $u -NoCommit
$n.Commit()
Remove-Module SMLets
You can read more about this from the below article
Change Assigned user with SMlets https://video2.skills-academy.com/en-us/answers/questions/410315/change-assigned-user-with-smlets.html
SCSM how to change assigned to of an incident from PowerShell https://social.technet.microsoft.com/Forums/ie/en-US/cc9ce2db-26a5-4a06-b3cb-490872ac43c5/scsm-how-to-change-assigned-to-of-an-incident-from-powershell?forum=systemcenterservicemanager
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