Hello TP link, 

I have now waited some time (like 2-3 years) for the option to be able to manually set the channels in my network since there are LOADS of networks in my surroundings that is actually giving a lot of disturbance in the channels that your software autoassign for my decos.

So my setup is the following. 

I have 3 m9 (1 router, 2 satelites). 
I have 1 SSID published "Aspegren", that I am sending on both 2,4 and 5 GHz band.
On 2,4 there is now 3 "accesspoints" that is sending on channel 1. 
And on 5 there is now 3 "accesspoints" that is sending on channel 36.

In my house I will therefor reach the same SSID over the same channel, but it comes from 3 accesspoints at the same time. 
Also, I am able to "see" like 25 more networks that is not belonging to me, and out of those there are at least 4-5 networks sending on the same channels as I do.

Network optimization is a cool feature, but it is not solving the issue since it is a dynamic feature that give some help at the time you are running it. 
But since the solution is not permanent, you will need to run it again and again and again.

As you can see in the below picture of my heat-survey, it cannot get more worse than this?!

I do understand that you want to keep it simple to get it up and running. 
But you could also have the "advanced option" for those users that will be able to manually configure and tweak their network

Please consider to release this feature.

Br. 
Martin Aspgren