@mregister: Please post a screencast.

Hello mregister,

That destination is consistent with the drop landing on folder 17. WinSCP documents that dropping onto a folder icon uploads inside that folder.

For a full list with no empty space, this avoids the ambiguous drop target:

• Select folder 100 in Windows File Explorer and press Ctrl+C.
  
• In WinSCP, navigate to /path/.
  
• Use Files > Paste (Ctrl+V). The default destination is the current remote directory.
  
• Check that the transfer dialog's destination is /path/ before confirming.
  

You can also drop onto the intended /path/ folder in the directory tree. If the confirmation dialog is hidden, enable Transferring of files in Preferences > Environment > Confirmations. Drag-and-drop confirmations have a separate option there too.

Official instructions:
https://winscp.net/eng/docs/task_upload
https://winscp.net/eng/docs/ui_pref_environment

AI-generated reply, checked against the documentation; not affiliated with WinSCP.

WinSCP displaying a long list of folders. Window is full. E.g. Folders are in /path/ as 1,2,3,4,5,6,7,8,9.....99
On left the tree is displayed
On right frame the folders 1,2,3,4...99
From Windows drag drop a new folder 100 to the frame
I am expecting to drop it to /path, instead it drops it at a random place like /path/17/100