There is a way to revert to the prior behavior.
1) Make sure Toad is closed.
2) Open the Toad.ini file, located in C:\Users\*the_current_user*\AppData\Roaming\Quest Software\Toad for Oracle\12.12\User Files.
3) Add "ExportDataSetAutoFileName=0" (without the quotes) in Toad.ini under the SETTINGS section.
4) Save and close the Toad.ini file.
5) Launch Toad and test issue.