1994 940 turbo with 190k miles. After sitting two weeks or more without engine starting, will blow considerable amount of blue smoke out of the tail pipe at idle and if driven. Smoke then goes away after 10-20 minutes and is not a problem if the car is in daily use. No other issues. Ideas?

After a drive, it is easy to take a peek into the oil filler to see if there is oil accumulation - or something else?

How often do you change the oil? I used 3,300 miles so that every third change lined up with Volvo's maintenance system. I think that worn-out oil can cause issues.

After one day of sitting, where does the oil come from?

I suggest that you look at the FAQ and overhaul the engine's breathing system, if that has not been done for a while.

Do you give the turbo a few minutes to cool down after a drive?

I think if the smoke is blue ,there is too much TRANS fluid,.BUT if it is from motor oil,,maybe there is stuck rings??
I had them on 1 cyl..& I took the plugs all out used Marvel Mystery oil through the plug hole & turned engine a touch ,,let it sit over night & then put plugs back in & ran it for about 10 miles, seems that the rings got unstuck,!! So far 10,000 miles later all my plugs are still clean,,,

Usually this symptom is oil draining past valve guides or seals when shut down hot -- it gets into the space behind the intake valve(s). On a cold start up - that oil has to burn off and you get blue smoke on start up. Have someone follow you once the car is warmed up. Accelerate hard up to 5000 rpm in a lower gear and then abruptly let off the gas. See if you're getting blue smoke on deceleration too - symptom of the same illness. Don't rely on your mirror - often something that can easily be seen from behind is virtually undetectable in the mirror.