I understood why I couldn't run apex in fse mode before. Now everything has become clear. If part of the functionality of the game mode is cut, the system does not define apex as a game and an entry in the GameConfigStore \ Children section does not appear in the registry. If the functionality of the game mode is full, then the entry in the registry appears automatically, if this does not happen automatically for some reason, the game can be added manually through the game bar "remember as a game".
And only then you can make changes that lead to fse.