Noticed while working on T5478: Kleopatra: Performance problems decrypting and encrypting large Archives.
Currently, Kleopatra happily starts the sign/encrypt operation if the archive file already exists. When the operation is almost completed, Kleopatra asks whether the existing file should be overwritten or the operation shall be canceled. With no way to save the file with a different name. (But, of course, the user can move the existing file out of the way if they want to keep it.)
This should be improved by checking for an already existing file before starting the operation.
Update: Checking for file name conflicts before starting the operation would defer the start of the operation. And we cannot be sure that no file name conflict occurs when a long running operation is finished. So, instead we offer the users to change the name of the result in case of a file name conflict.