It seems to be a general problem with bottom placed panels. Out of interest, I tried running Compiz alongside KDE Plasma 5 and I noticed that the launcher menu there was also offset. I've added a very brief section about this to the Arch Wiki.
It seems to be a general problem with bottom placed panels. Out of interest, I tried running Compiz alongside KDE Plasma 5 and I noticed that the launcher menu there was also offset. I've added a very brief section about this to the Arch Wiki.