There are no settings for Menu File Save (Ctrl+S). However, if you opened a flat File and add layers to the open document in Photoshop. If you use File>Save Photoshop will switch to File Save AS to give you the opportunity to save a layer file like a PSD or PSB. If you Flatten or merge all layer the document before you use File>Save. File>Save will not switch to Save As the File you Open will be overwritten with your updated document content.