Hi LittleOwl and welcome.
I suppose you mean this one: 12. A new option was added on "Merchant/Warship/... spotted" popup window. By checking this check box (called "Set as default action") the selected action will be always performed when the situation occurs. This default action will be saved from a game to other and can be reset, during the game (when press ESC) by choosing "Options/Reset default action" from Game options;
You can not access the popup window itself by pressing ESC and go to Options.
It will popup during gameplay when your crew spots enemy ships or planes. As you may perhaps found out yourself by now:hmm:
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