We seem to be at cross purposes here. I have no problems with making filters. My problem is that I don't know how to *filter the mail manually*.
Let's say you make a filter for all mail containing the address x@y.x to go into the X mailbox. You set it to filter in three ways: incoming, outgoing, and *manual*.
From now on, all the mail that comes in, and all the mail you send out, is filtered into the mailbox you've made and called X.
But what about all those 50 mails from your friend X? You'd like to filter those in manually.
In my old Eudora, you simply highlighted the whole mailbox and pressed cmd-j, and all the mail in that mailbox trotted off into the different mailboxes you'd instructed the filter to send it to. So the mails from X would go to mailbox X, the mails from that fascinating maillist Mailfilter-L would go into the mailbox you'd called Mailly, etc.
It's this latter business I can't do - the actual *manual* use of the filter. And the menus are no help to me, unfortunately. Can't find any reference to manual filtering in them.