A slerp is just a linear lerp between two quaternions (and then normalize the result).
i.e. R = Q1 + t * (Q2 - Q1)
The result of R will range from Q1 to Q2 while t ranges from 0 to 1. You can make this computation every frame yourself in a task and then apply R to whatever node you like.
Or, you can have Panda do it for you with something like a LerpQuatInterval.
David