How to move, resize or remove KDE widgets since Plasma 5.5.5 (xenial) [duplicate]
Solution 1:
With Plasma 5.5.5 the menu appears after a long left-click (instead of hovering with the mouse in Plasma 5.4.2). This can be changed back in Desktop Settings (right click on desktop) -> Tweaks -> Widget Handling. This solution was first posted on bugs.kde.org.