For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:wolfi323:branches:home:dliw/15.6/home:wolfi323:branches:home:dliw.repo
zypper refresh
zypper install mysql-workbench
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:wolfi323:branches:home:dliw/15.5/home:wolfi323:branches:home:dliw.repo
zypper refresh
zypper install mysql-workbench
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:wolfi323:branches:home:dliw/15.4/home:wolfi323:branches:home:dliw.repo
zypper refresh
zypper install mysql-workbench