How to remove unneeded file masks

I create a lot of one-time file masks to speed searching for files. How do I delete the unneeded ones? Replacing an old file mask with a new one using Edit doesn't work--the new mask is created but the old mask is retained. So where does the mask file reside? I can't seem to find it but I figure if its a text file I could edit it. Thanks in advance.

Using version 5.14.4.

John

All edit boxes histories are stored in your configuration storage, which is by default located in Windows Registry (unless you have switched to an INI file).
The Registry key is:
HKEY_CURRENT_USER\Software\Martin Prikryl\WinSCP 2\Configuration\History\Mask

In WinSCP GUI you can only delete whole history, using Ctrl+Del, while the particular history is dropped down.