As @WanWizard wrote before me - the right question is how did you turn off your set-top box. Do you mean the power switch on the set-top box ? Or did you simply switch the set-top box to standby mode with the help of the RCU (with the help of Enigma2 / GUI) ? Or another way to turn it off - for example, through a terminal connection or through the OpenWebif interface ?
It also depends on what or what style you have edited your list of favorite channels. Did you edit this channel list directly in Enigma2 / GUI, with the help of RCU ? If so, this list is saved only during certain events. Otherwise, the list remains only in the data area of the Enigma2 memory, but not on the internal disk. If I'm not mistaken, only when you use the standby mode of the set-top box, only then is the modified list of your channels saved on the internal disk.