Version:            (using KDE KDE 3.4.1)
Installed from:    Gentoo Packages
Compiler:          gcc 3.3.5-20050130 
OS:                Linux

Something like this has already been discussed in http://bugs.kde.org/show_bug.cgi?id=89221, where I added a comment but didn't get noticed. I removed/deleted the buttons (mark as SPAM/HAM) generated through the wizard via the toolbar configuration screen. I wasn't able to bring them back so I checked bugs.kde.org and saw this is not new. In my case now I'm not able to add any filter action button to the toolbar - even filters not generated by any wizard. The filter action buttons are listed on the left hand side in the toolbar configuration screen and I can add them to the right hand side, so they may show up on the toolbar, but they simply don't show up. As well as any assigned shortcuts for these generated filter actions (e.g. mark as SPAM/HAM) won't trigger after a restart of Kmail - I have to reassign them. I'm no expert at all, but the action of removing buttons from a toolbar has never ever had a semantic meaning like deleting a file - even if there is a warning message, which hardly anyone reads since any message other than "Accept the changes?" isn't expected (just my 2c).