Yes you can put 2 diapers on a baby or toddler at night to increase the absorbency of the diaper if your baby or toddler wets heavily at night.
When my son was 3 years old he would wet a lot and soak through one diaper so I started diaper diapering him at night to help increase the absorbency of the diaper he was wearing.
What I did was take the first diaper and before putting it on him I would cut a few slits in the front of the diaper so that the pee would soak through the first diaper and go into the second diaper.
After cutting the first diaper with slits in the front you can then put it on the baby or toddler like normal.
Then just apply the second diaper over the first diaper and the diapers absorbency will be increased for the night.
Sometimes I would do that on long road trips as well especially if the kid would fall asleep and wet and we couldn't stop in time to change his diaper.
It made the diapers thicker though so the child or baby might need bigger pants or clothing to fit over the diaper.
But at night you can always let the baby or toddler sleep in just the diaper unless it's chilly in your house but then a pair of pajamas should easily fit over the diapers.