Hi!
I created a simple rocket with onion (or is it asparagus?) skin staging. (The central rocket was surrounded by 4 liquid fuel boosters. One group of boosters led into the other boosters, and those led into the central column).
Each set of two boosters and their decouplers were added separately, with the idea being to jettison one group of boosters first, followed by the second. Unfortunately the staging tools combined the decouplers so I was unable to do this as intended via the staging system. I got around it by pausing the game once the first set of boosters ran out of fuel and manually engaged the first set of decouplers.