"I enable in the add-0n airport config but IF disable it after starting flight."
Addon-Airports Configuration in the popup menu - you disable things in there. Any scenery you don't want changed or maintained by auto-scenery you uncheck in there! Very simple.
"A button on the flight planning page with asscess to the add-on airport config would be great.
Just a little airport scenery manager."
That's not such a good idea. You need to set and forget, you don't want to be changing stuff around. Then IF just enables the two airports, AI is recomputed to use the stock airports where they are disabled.
"I like to see scenery from 6 to 11 thousand feet so I need whatever am flying over to be active."
That would be everything enabled so simply don't have auto-scenery enabled. Scenery outside the bubble isn't an effect.