I wrote a small (5K) C program, tc2freedesktop which creates freedesktop.org compatible menus in /usr/local/share/applications based on WBAR entries in /usr/local/tce.icons for Xfce4 or other compatible desktops. This means that applications with WBAR entry will be visible in Xfce4 menu system also without extra adaptation. If they provide a proper menu by default it will be used. It doesn't overwrite nor delete existing entries.
As TC entries do not have category, programs are placed to the same category, System. On Xfce4 add it to 'Application Autostart' list in 'Session and Startup' setting menu.
tc2freedesktop.tcz posted for submission.
Cooments are appreciated.