Bulk Update SailPoint IdentityNow Entities Manager Attribute via API and PowerShell. Associated Blog Post https://blog.darrenjrobinson.com/lifecycle-management-of-identities-in-sailpoint-identitynow-via-api-and-powershell/

Update SailPoint Identities Managers.ps1

# Your API Client ID
$clientID = 'yourClientID'
# Your API Client Secret
$clientSecret = 'yourClientSecret'
$Bytes = [System.Text.Encoding]::utf8.GetBytes("$($clientID):$($clientSecret)")
$encodedAuth = [Convert]::ToBase64String($Bytes)
# Your IdentityNow Tenant Name
$orgName = 'yourTenantOrgName'
$searchLimit = '1000'
# Source Name in IdentityNow that contains the Accounts that will be updated
$sourceName = "External Entities"
# Queries for all users in NSW to update with a Manager
$query = 'attributes.state:NSW'
# Search URI
$URI = "https://$($orgName).api.identitynow.com/v2/search/identities?"
# Update Accounts Base URI
$updateBaseURI = "https://$($orgName).api.identitynow.com/v2/accounts/"

# Search Accounts to update Mgr for 
$searchResults = Invoke-RestMethod -Method Get -Uri "$($URI)limit=$($searchLimit)&query=$($query)" -Headers @{Authorization = "Basic $($encodedAuth)" } 
write-host "$($searchResults.Count) found"

# Mgr to find 
$manager = "Rick Sanchez"
$queryManager = "attributes.displayName:" + '"' + "$($manager)" + '"'
# Search for Manager
$mgrSearchResults = Invoke-RestMethod -Method Get -Uri "$($URI)limit=$($searchLimit)&query=$($queryManager)" -Headers @{Authorization = "Basic $($encodedAuth)" } 
write-host "$($mgrSearchResults.Count) found"

if ($mgrSearchResults.Count -eq 1) {
    foreach ($identity in $mgrSearchResults) {
        Write-host "Manager $($identity.displayName)"
        $mgrID = $null
        foreach ($account in $mgrSearchResults.accounts) {
            If ($account.source.name.Equals($sourceName)) {
                $mgrId = $account.accountId 
            }
        }
    }
}

# Update Users with Manager     
foreach ($identity in $SearchResults) {
    Write-host "Updating Manager for: $($identity.displayName)"
    $id = $null 
    foreach ($account in $identity.accounts) {
        If ($account.source.name.Equals($sourceName)) {
            $id = $account.id 
        }
    }

    if ($id -and $mgrid) {
        $updateURI = "$updateBaseURI$($id)?org=$($orgName)"

        $body = @{
            "manager" = $mgrId
        }
        $body = $body | ConvertTo-Json

        try {
            Invoke-RestMethod -Uri $updateURI -Method Patch -Body $body -Headers @{Authorization = "Basic $($encodedAuth)"; 'Content-Type' = 'application/json' } 
        }
        catch {
            write-host -forgroundcolor yellow "Well, that didn't work. Check your script"
        }
    }
}