Hi Ian,
For an intensity flicker, I'd first recommend trying an automatic effect, rather than programming a chase.
If you want to add an intensity flicker to a cue, go into the cue, so that it is live onstage. Then select your LED fixture, scroll the tabs along the top, and choose the "Effects" tab. Tap "Automatically Create Effect Palettes" if you haven't already. Then tap Effect 9, which is a candle effect. You can then adjust the speed and size of the effect using the encoder wheels, until you achieve the flicker you are after. To add colour to the fixture, try adding Effect 39 too, which is the fire effect. Once you are happy with the scene on stage, tap UPDATE, and tap your playback's GO button, to add your changes to the current cue.
If you do wish to add a chase to a cue in the master playback, please see the link below for more information...
https://www.zero88.com/manuals/zeros/cues-playbacks/chases
I hope this helps. Let me know if you have any questions.
Edward