Hey Benoit,
Do you have a recommendation for the best way of accomplishing this? I have a few sets of living room can lights I would like to group together and dim to various levels. I have been using the device groups within the Alexa app and noticed the delays you're speaking of. I'm some what of a newbie to ISY and my only thought was to create an scene for each dimmer level (i.e. 10%,20%,30%,etc). Only issue I see with that is the spoken context. I would no longer be asking Alexa to dim the lights to 20%, I would not being saying "Alexa, turn on 20%."
Curious to hear your thoughts. I would like to keep things as natural sounding as possible so others are able to quickly pick up on the commands.
Thank you,
Brandon