It would be nice to have an additional toolbar (View > Toolbars) called Custom Toolbar.
On this toolbar, you would be able to specify which of the existing toolbar buttons (from the other toolbars) could be displayed on it.
For example, I want to create a custom toolbar that has Parent Driectory button, Refresh button, Add/Edit Link button, Open Session in PuTTY button, Find Files button, and Open Saved Session dropdown. This way I can hide all the other toolbars, and only show my custom toolbar with the specific buttons I want to use.
Perhaps a new section could be added in the WinSCP.ini file called [Custom Toolbar] and ALL existing toolbar buttons would be listed with a default of false. meaning the custom toolbar would be empty as the default setting. Setting any of these to true would make them display on the Custom Toolbar. So it might look something like this:
Address.AddressDropdown = false
Address.OpenDirectoryBookmark = false
Standard_Buttons.Back = false
Standard_Buttons.Forward = false
Standard_Buttons.ParentDirectory = false
Session_Buttons.NewSession = false
Session_Buttons.DuplicateSession = false