Q:

How to restore horizontal application menu in KDE Plasma 5? 

I would like to restore the horizontal style in-application menu bar in KDE Plasma 5.  Somehow I ended up with a single "control" menu item like this:

Using that requires two mouse clicks instead of one.  
What I would like is the horizontal style in-application menu (just below the title bar) like this:

What are the steps for switching back? 
The other questions on this topic discuss Global Menus, which I do not believe is related to my question about in-application menus.  I am not using global (Unity or Mac style) menus. 
Other questions / answers I looked at include:

https://unix.stackexchange.com/a/426002 
https://unix.stackexchange.com/a/489727
https://askubuntu.com/questions/30180/menubar-hidden-in-all-kde-apps

Pressing CTRL-M does not resolve it.  That appears to be a different issue.  I have a menu, it's just not the one I want. 

A:

Operating System: Kubuntu 19.04
KDE Plasma Version: 5.15.5
KDE Frameworks Version: 5.57.0
Qt Version: 5.12.2
Kernel Version: 5.0.0-15-generic
OS Type: 64-bit

I've checked with Dolphin, Kate and Gwenview.  
I think the problem is with the ☰ button in your title bar.  Its presence suppresses the appearance of the horizontal menu. 
Remove it by opening System Settings > Application Style > Window Decorations > Buttons tab and dragging the ☰ button off your title bar into the space below. 
In Kate and Gwenview, the horizontal menu now can be toggled on/off with Ctrl+M.
In Dolphin, now Ctrl+M toggles between the horizontal menu and the Control (☰) button. 

Edit 
And it's the same with the Fedora 30 KDE Spin:
Operating System: Fedora 30
KDE Plasma Version: 5.15.5
KDE Frameworks Version: 5.58.0
Qt Version: 5.12.1
Kernel Version: 5.0.17-300.fc30.x86_64
OS Type: 64-bit

