Official comment
It takes a couple of steps to do this, but here's the best way to do it...
In the LIGHTING mode, go to the MACRO MAPPING tab and select the bank you want (HIGH / MID / LOW), and choose one of the energy levels (eg. COOL, because it's the first one on the list), then drag your custom user scene into the position for whichever particular phrase you want to override. This doesn't affect the mapping for previous uses of this scene, so other songs won't be changed.
So let's say you've created several custom scenes, you can go and drag those into the INTRO, VERSE1, CHORUS, UP, DOWN, BRIDGE, OUTRO scenes for COOL of all three HIGH / MID / LOW.
Once you're back in PERFORMANCE mode, you can then right-click on the lighting thumbnail of the track that's been loaded, and select the first one on the list (the grey looking scene thumbnail) - that will be your custom one. The reason I suggested you do this for all HIGH / MID / LOW is that you can't toggle the energy level of the song in performance mode, but this would at least give you access to change the lighting macros on the song itself.
Let me know if you have any questions about how this was done.