How long should one let the motor turn (witout driving) to re-charge the car battery, after having using it to charge a laptop's battery
For the sake of estimate, let's assume the following:

Battery charge current = 0.1C = 0.1*60A = 6A max
Starter current is 200A x 3 seconds

When you start the car, you consume:

200A * 3s / 3600s = 0.17 Ah per start

Your estimated laptop charge is 120 Wh, or conservatively about 10 Ah per complete charge from the car battery.
So the total consumption to charge the battery, then start the car is:

10 Ah + 0.17 Ah = 10.17 Ah.

Charging rate is the 0.1C rate of 6A, so:

10.17Ah / 6A = 1.695h or 102 minutes.