Ini must have read my mind or been cooking up autosave in the background im happy its finally in the plane and its effective and fast.
The Autosave is on the Main page of the OIS if i remember correctly its under the Utility list like 2nd from last or something.
or do you mean where are the autosave files saved for the A350? if so you will find them here C:\Users\AppData\Roaming\Microsoft Flight Simulator\Packages\inibuilds-aircraft-a350\work\autosaves, the autosave seems to keep about 4 or 5 of your last autosaves and deletes the oldest one automatically when a new 4th or 5th save is done which is cool and you can make your own custom auto saves at any point.
Thank you @iniBuildsfor adding this, helped me to be able to do my 1st Ultra Long haul yesterday at 15hrs,
Big Love From Me