/usr/bin/xfce4-accessibility-settings
/usr/bin/xfce4-appearance-settings
/usr/bin/xfce4-display-settings
/usr/bin/xfce4-keyboard-settings
/usr/bin/xfce4-mime-settings
/usr/bin/xfce4-mouse-settings
/usr/bin/xfce4-settings-editor
/usr/bin/xfce4-settings-manager
/usr/bin/xfsettingsd
You may install this package on Debian with
apt-get
install xfce4-settings