Variable Start / End Times for Flux Component?

I want to create my own circadian-ish automation and I’m curious if there’s a way to utilize the Flux component to do what I’m thinking. What I’m looking to do is:

1 hour before Sunset start dimming XYZ lights so they achieve ABC brightness at sunset. The catch is that I only want it to dim lights in the XYZ group if they are on, and I want it to ignore lights that are off (which is preventing me from simply setting a scene with a transition).

Which brings me to the flux component. Is it possible to setup something like this? I just don’t know how to define [sunset +/- 1 hour].

  - platform: flux
    lights:
      - light.xyz
    name: XYZ Flux
    start_time:  [sunset -1 hour]
    stop_time:  [sunset]
    transition: 30
    interval: 60