function Get-UserProcess($ProcName) {
    $owners = @{}
    gwmi win32_process |% {$owners[$_.handle] = $_.getowner().user}
    $result = get-process | select processname,Id,@{l="Owner";e={$owners[$_.id.tostring()]}} | Where ({$_.Owner -eq $env:USERNAME -and $_.processname -eq $ProcName})
    return $result
}

Start-Process -FilePath "путь\к\плагину.exe"
Start-Sleep -s 2
Start-Process -FilePath "путь\к\1c.exe"

$target = "название процесса 1c"
$process = Get-UserProcess $target
while ($true)
{
while (!($process))
{
$process = Get-UserProcess $target
start-sleep -s 5
}
if ($process)
{
$process.WaitForExit()
start-sleep -s 2
$process = Get-UserProcess | Where-Object {$_.ProcessName -eq $target}
Stop-Process -Name "название_процесса_плагина" -Force
}
}