After installing the KDiff3 application (or another KDE4 application) it is not appearing in application menu. PS: Discussion on bugzilla.opensuse.org: https://bugzilla.opensuse.org/show_bug.cgi?id=1062437
Thanks for the report. I've just tested on KDE Neon and installed kdiff3 and it's showing in my menu. Can you please test and confirm if this issue is still occurring or if this bug report can be marked as resolved. I'm setting status to "needsinfo" pending your response, please change back to "reported" when you respond, thanks.
I ran a test on a newly installed OpenSUSE Leap 15.2 KDE. The kdiff3 appeared in the main menu after installation. This bug report can be marked as resolved.