I was just trying to use the "Server Configuration -> Website Redirects" function to create an http->https redirect. I found that that function adds the redirects to both the SSL and non-SSL virtual host.
Suggestion: Allow the user to choose whether a redirect created with that function goes to the non-SSL and/or SSL virtual host.
(I know I can create the redirects directly in Webmin's Apache module, but well, you know... Virtualmin is about comfort. ;) )