I know I can do this in rule machine (which is what I'm doing), but when the trigger is sunrise or sunset the app only has the option to turn on/off again at sunset/sunrise. Is it possible to include a turn on/turn off time as well?
You can already do this: you just need a separate Simple Lighting child app, so one for your "on" time and one for "off." 
(People used to say "rules are free" back when Rule Machine was less powerful than it is now and you often needed multiple rules to accomplish one result. Nobody ever said "Simple Lighting child apps are free," but, hey, the same applies.)
This feature has been requested a few times before, but it's not clear they have plans to add it (at some point, I guess it would stop becoming "Simple Lighting").
Thanks, I used to do that but recently replaced them with a single rule (as my proficiency in RM improved).
I guess this feature made sense to me in that you often want to turn an outside light on at sunset but not leave it for the whole night. But it's no biggie 
