Menu path: Setup > User Interface > Desktop > Screen Lock/Saver > Taskbar

Taskbar settings when the logon dialog is visible:

Show taskbar during the logon dialog (default)

Taskbar settings when the screen is locked:

Show taskbar when the screen is locked (default)

No taskbar is shown for the locked screen, the taskbar is visible in the logon dialog and allows an on-screen keyboard, e.g. for touchscreen monitors, to be shown.