No I am not using Amazon Echo.
I think I jumped to conclusion little early. Smart Lighting app only set Dimmer to one level - 10%,20%,30%… etc. So I don’t think there is a way to control the amount of dim using Smart Lighting App. So as @quantiletree pointed out earlier in this thread, Smart Light App may not be the solution, if I want to dim group of lights to what ever I want. (I think this is basic functionality to have out of the box in ST). Answer may still be, 1. Virtual Dimmer device & 2. Dim with Me App. Not sure if there any other ST out of the box hidden work around.
However now that I got into exploring the ST more (Have become a hobby now), will give it a try with “Rule Machine”. In fact I was wondering how to implement AND, OR conditions in ST and Rule Engine may be the answer. Thank you for bringing it up.
As you can see I am just getting warmed up, and finding out why lot of things which are simple but not implemented out there 
Appreciate all the feedback.