package-update-indicator from home:manfred-h:X11:xfce:4.18 project
Select Your Operating System
Add repository and install manually
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:manfred-h:X11:xfce:4.18/15.6/home:manfred-h:X11:xfce:4.18.repo zypper refresh zypper install package-update-indicator