Configuration Manager (SCCM) | OSD | Task Sequence Pause
Sometimes, you may wish to Pause a Task Sequence, especially when using a Boot Image with the Option ‘Enable command support (testing only)‘ enabled

This can be easily achieved by running a simple PowerShell script

# Hide Progress Bar
$TSProgressUI = new-object -comobject Microsoft.SMS.TSProgressUI
$TSProgressUI.CloseProgressDialog()
# Load assembly
Add-Type -AssemblyName PresentationCore,PresentationFramework
# Set message parameters
$msgBody = "Have a break, have a ……. and select OK when ready to resume!"
$msgTitle = ""
$msgButton = 'OK' # OK, OKCancel, YesNoCancel, YesNo
$msgImage = 'None' # None, Error, Question, Warning, Information
# Create message box
$Result = [System.Windows.MessageBox]::Show($msgBody,$msgTitle,$msgButton,$msgImage)
Better still if you are using Configuration Manager 1906 (SCCM) or later then check at the Microsoft Debug a task sequence ( although still in preview )
https://docs.microsoft.com/en-us/mem/configmgr/osd/deploy-use/debug-task-sequence