Thanks for your post.

This request is being tracked already:
https://winscp.net/tracker/1168

Currently you can mass-modify all stored sites using /batchsettings command-line parameter:
https://winscp.net/eng/docs/commandline#batchsettings

Hy,

is it possible to confiugre a Proxyserver which works fpr the whole program and all connections. At the moment I have the problem when taking my Notebook to work, I have to change the connectionsettings of all connections. It would be much easier to have one central Proxy option.