1- Does this mean Turkish Do&Co is added to GSX? Because if it is, I don’t get it in the sim. Only catering I options I see are gate gourmet and Servair at these locations.
I can see them at every airport in Turkey, see the attached screenshot at LTBA ( new Istanbul doesn't exist in P3D default scenery ).
2- We are talking about Turkish Do&Co not parent company DO&CO right?
The DO&CO parent company. Each new livery adds lots of Simobjects and slow down startup so, in case of multinational companies, we tend to use only the parent livery, otherwise the number of variations would explode. DO&CO truck has several major city names on its livery, including "Istanbul" so, I guess it's appropriate enough.
I see that there is Do&Co texture available in the catering simobjects folders however i do not see any entry for this neither in sim.cfg or catering config file (which airports its used in etc.)
You will never find any airports in the SIM.CFG of the catering vehicle. Every vehicle class in GSX is assigned by its own "rules" file in the Addon Manager\texture folder and, sure enough, the rules_catering.cfg file has this line for DO&CO:
[DoCo]
couatl.atc_parking_codes = Do&Co Catering
couatl.icaoprefixes = ? E K LT LTFM KJFK KLGA EGLL EGKK LEBL LIM EDDB EDDF EDDM LOWS LOWW
couatl.basecolor = cool_grey
Which means, they'll appear everywhere in Turkey ( LT code ) and since there are not any more specific assignment in that file with more than 2 letters for LT, they'll always appear and will be the only catering available.
And in fact, when I tried to make the screenshot, Do&Co appeared without even showing a menu, which is how's supposed to work when there's only one candidate available.