First, clean the engine. Try to cover up electrical connectors and the alternator, remove the battery. This is a good time to clean the whole engine bay. Spray with degreaser and soapy water. It will make finding the leak 1000 times easier.
The problem is that once there's a leak, air blows the oil all around. So sometimes oil moves down, sometimes it moves towards the back of the car.
Try looking at the back of the valve cover and the EGR weep hole.
The turbo can leak but if the exhaust is normal and not smokey, it's probably an external leak. The EGR weep hole often leaks oil, this is very common. As it drips down, it coats the back of the engine.
I know that there are dyes that you can add to the oil, not sure if it's approved for diesels. The idea is that you add a dye, drive the car, and then use a special light to see where the dye has stained the exisitng oil leaks.
They use a UV or blacklight to detect the dye. Some have special tinted glasses to make the colors stand out more. I don't see why it wouldn't be compatible with diesel oil but I would change it out as soon as you can just in case. If the leak is bad, you don't want it dripping down onto the hot exhaust either.
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