Ctrl+Alt+H

Hello,

I am using WinSCP for the first time. The Ctrl+Alt+H designed to show hidden files seems to work for only one side(left side) of the software. How do I make it work for both?

It works for both panels. If it does not show the hidden files, it's because the server does not send them to WinSCP. Can you see the hidden files using any other client?
If you are using FTP protocol, you can also try turning off use of MLSD command.
See also https://winscp.net/eng/docs/ui_file_panel#hidden_files