@Rockwell: Your related post on Super User:
WinSCP auto Synchronization files of local subfolders directly into root's remote

Hey Martin! I could load the extension into the WinSCP but can't figure how to run this to the actual synchronization.

You can write a simple PowerShell script for that.
We have an example for download:
https://winscp.net/eng/docs/script_download_files_to_same_folder

Upload would be similar.

Actually, this code will do what you want:
https://winscp.net/eng/docs/library_example_moves_files_keeping_directory_structure#upload_powershell
If you modify it to:
1) replace $remoteFilePath with $remotePath in the $session.PutFiles call
2) remove if (!($session.FileExists($remoteFilePath))) { $session.CreateDirectory($remoteFilePath) }

It's just unnecessarily complicated for your simpler needs.
On the other hand, it's prepared to be used as a WinSCP extension, so it can be installed into WinSCP GUI.
https://winscp.net/eng/docs/extension

For a simple code, see
https://stackoverflow.com/q/43716807/850848

Hello,

Is it possible to ignore local directory file structure when copying files?
Let's say we've got a couple of files in subdirectories as follows:


Is there a way to put those 'testa*.txt' files on FTP server without copying the folder structure. Ideally, I would like all the files to be dropped into a single folder on the FTP server, is there a way to do it?

Thanks
Cristiano