See this forums entry here: https://forum.kde.org/viewtopic.php?f=223&t=140139#p381708
In essence, this bug requests the ability to create toolbar buttons that execute arbitrary commands. This isn't limited to Dolphin; the feature would probably be added to the generic "configure toolbar" dialog that most KDE apps use.
OK, thanks a lot.
*** Bug 392802 has been marked as a duplicate of this bug. ***
I would also love this.