No, that is not possible. If you choose to open a file in an external application then this file will always be saved in the temp folder. If you want to store the file elsewhere then you would have to download the file to both locations or open the file from that other location. Files downloaded to the temp folder are saved as read-only because it isn't guaranteed that this file is not removed and you may lose changes and if you want to modify such a file then you need to save the file to another location via "Save As".