Para openSUSE Tumbleweed ejecute lo siguiente como root:
zypper addrepo https://download.opensuse.org/repositories/home:AndnoVember:XFCE/openSUSE_Tumbleweed/home:AndnoVember:XFCE.repo
zypper refresh
zypper install gtk-xfce-engine
Para openSUSE Leap 15.2 ejecute lo siguiente como root:
zypper addrepo https://download.opensuse.org/repositories/home:AndnoVember:XFCE/openSUSE_Leap_15.2/home:AndnoVember:XFCE.repo
zypper refresh
zypper install gtk-xfce-engine
Para openSUSE Leap 15.1 ejecute lo siguiente como root:
zypper addrepo https://download.opensuse.org/repositories/home:AndnoVember:XFCE/openSUSE_Leap_15.1/home:AndnoVember:XFCE.repo
zypper refresh
zypper install gtk-xfce-engine