I see there is rising demand for integrating time tracking into Mantis. We've been using Mantis with our own patch for about 2 years.
I'll release this patch with screenshots as soon as version 0.19.1 is released.
 
The patch is more a "proof of concept"-implementation and should be a starting point of further discussions for how to implement this into Mantis.
 
Regards,
Espen Holje