This is a tricky question for a couple of reasons.
LightBurn is usually set up to Gray-out options that aren’t available and make options that aren’t applicable disappear entirely.
When you say ‘Job complete clock’, I think you may be referring to the Progress bar for file transfer for GCode devices.
On a fiber/galvo set up there are Simulation Settings on the tab behind Device Settings. With these Simulation Settings filled in, there would be an elapsed time (estimate) available in the Preview window but i’m not seeing the Job Complete clock.