How to automatically rename when uploading files

When uploading a file, if the following two conditions are met at the same time, the old file name will be automatically renamed:

1. The file names are the same
   
2. File sizes are different
   

For example, paper1.txt, if the file is uploaded again and meets the above two conditions, it will become paper1.txt, paper1(1).txt. If you upload it again and meet the above two conditions, it will become paper1.txt, paper1(1).txt, paper1(2).txt. And so on.

Sorry, but no, WinSCP cannot fulfil your arbitrary conditions.

Similar functionality is WinSCP's recycle bin:
https://winscp.net/eng/docs/ui_login_recycle_bin

If you specify the current working directory (".") as the recycle bin path, the behaviour will be similar to what you ask for. Except for the naming convention. And on overwrite it works with SFTP protocol only.

This is also a good design and I will take advantage of it.