I don't know if there is a faster way to do it but here is how i would do it.
First you cast healing wave and it hit 1 target
then create dummy unit on target location, and let it cast another healing wave to random target from the dummy position
make the healing from triggers so healing wave should not heal it is just a dummy, if you want it to jump more times just do it again spawn 1 dummy from the next target and let it cast healing wave to random target.
You need to make the dummy spawn on the target each time to make it look like healing wave, but the random target could be from the position of caster.
and to make sure it doesn't hit the same target twice just add the targets to unit group and make a condition to not be in that group.