Powershell – How to modify an existing scheduled task using Powershell

I am working on some release automation scripts that use Powershell to update existing scheduled tasks which execute various applications. In my script, I can set the Path and Working Directory of the application, but it doesn't seem to save the changes back to the task.

function CreateOrUpdateTaskRunner {
    param (
        [Parameter(Mandatory = $TRUE, Position = 1)][string]$PackageName,
        [Parameter(Mandatory = $TRUE, Position = 2)][Version]$Version,
        [Parameter(Mandatory = $TRUE, Position = 3)][string]$ReleaseDirectory
    )

    $taskScheduler = New-Object -ComObject Schedule.Service
    $taskScheduler.Connect("localhost")
    $taskFolder = $taskScheduler.GetFolder('\')

    foreach ($task in $taskFolder.GetTasks(0)) {

        # Check each action to see if it references the current package
        foreach ($action in $task.Definition.Actions) {

            # Ignore actions that do not execute code (e.g. send email, show message)
            if ($action.Type -ne 0) {
                continue
            }

            # Ignore actions that do not execute the specified task runner
            if ($action.WorkingDirectory -NotMatch $application) {
                continue
            }

            # Find the executable
            $path = Join-Path $ReleaseDirectory -ChildPath $application | Join-Path -ChildPath $Version
            $exe = Get-ChildItem $path -Filter "*.exe" | Select -First 1

            # Update the action with the new working directory and executable
            $action.WorkingDirectory = $exe.DirectoryName
            $action.Path = $exe.FullName
        }
    }
}

I have so far been unable to find an obvious Save function in the documentation (https://msdn.microsoft.com/en-us/library/windows/desktop/aa383607(v=vs.85).aspx). Am I taking the wrong approach here, and need to mess around with the task XML?