You need to run the remove powershell command with path of scope. you have to provide full path.
also run the below powershell to check all the available scope
param([parameter(mandatory=$true)][string]$Endpoint, [string]$Path = "/", [string]$Parent = "None")
[Reflection.Assembly]::Load("Microsoft.Workflow.Client, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35") | Out-Null
Write-Output ""
function WriteScopeInfo([string]$scopeUri, [string]$path, [string]$parent) {
$scopePath = $scopeUri + $path
$client = New-Object -TypeName "Microsoft.Workflow.Client.WorkflowManagementClient" -ArgumentList $scopePath
$manager = $client.CurrentScope
$scope = $manager.Get()
Write-Output "Name: `t`t`t$($scope.DisplayName)"
Write-Output "Path: `t`t`t$($scope.Path)"
Write-Output "Status: `t`t$($scope.Status.ToString())"
Write-Output "User Comments: `t$($scope.UserComments)"
Write-Output "Parent: `t`t$parent"
Write-Output "Children: `t`t$($scope.ChildScopeCount)"
Write-Output ""
if ($scope.ChildScopeCount -gt 0) {
$manager.GetChildScopes() | % { WriteScopeInfo $scopeUri $_.Path $scope.Path }
}
}
WriteScopeInfo $Endpoint $Path $Parent
https://lennytech.wordpress.com/2013/08/12/listing-all-scopes-in-a-workflow-manager-instance-using-powershell/