Nissan Primera P12: blueish grey smoke

Engine: f9q, 1.9dci

After driving for 90 minutes, mostly on motorways my car was leaving a blueish grey smoke all over the parking lot. I did not notice any smoke in the mirrors before I got to the parking. But while looking for a free parking space it was a lot of it.
About 10 minutes before parking there was a long steep uphill where the car needs to run in 4th gear (6 speed manual) at 2800rpm and almost full throttle for 2km to keep up with the traffic on the motorway. In other words, it had been pushed near its maximum about 10 minutes before entering the parking lot.

After being parked for about 30 minutes I checked all fluids before driving for another hour. I drove very carefully, and did not see any smoke - not even when looking straight onto the exhaust pipe.
Next I drove for one more hour towing a 900kg trailer - and still no smoke.

While driving I also kept an eye on ODB2 live readings, without seeing anything not normal.

Should I bee worried about the one incident where it smoked so much?
Anything I should do before going for the next long distance driving?

Hopefully it's not trying to tell me that the turbo will fail shortly.... or head gasket. I don't want to be far from home when any of those happens.

Could it have been water in the diesel?
I see water moving in a tube above the engine. I suspect it's extracted from the fuel filter. Maybe some water got passed the filter when the engine was pushed hard?

The strange thing is that it was smoking when idling in the parking lot, all the time until engine was stopped. After 30 minutes with engine off, there were no smoke at all when starting. I'd expect the level of smoke to go down when idling before stop.

If we're thinking of the same tube (transparent), I have a lot of air in the fuel line!Is there any way to bleed?