Using KDE
I accessed System Settings->Configure Desktop->Hardwere->Input Devices->Mouse
And I set the mouse to take action when I double-click
But it already triggers immediately when I click only once on the desKtop icons
How do I make desktop icons only trigger when I double-click?
Have a look in Workspace behaviour in systemsettings.
Sorry, but I did not find anything to configure mouse click behavior
The only place that says anything about the mouse is what I described before.
Could you show the way?
System Settings>Workspace>Desktop Behaviour
On Leap 15 I have:
System Settings>Workspace>Desktop Behaviour
Ande after that, I have>
Workspace, DeskTop Effects, Screen Edges, Touch Screen, Screen Locking, Virtual DeskTops, and Activities
I looked carefully all the parts and found nothing on double or single click
Probably difference between Leap and Tumbleweed’s KDE versions.
Yes, I’m pretty sure that’s the correct setting.
It works for me (requires double click) in Dolphin, in System Settings and for desktop icons. But it does not work in Yast – maybe that uses root configuration.
However, I’ve reverted to single click, since that’s what I prefer.
It is indeed. Run
kdesu systemsettings5
if you want that changed too. Which you don’t 
I also prefer less RSI ;).
So who prefers double click will not have a chance.
We are condemned to use simple click…that’s right?
See if this YouTube “how to” video helps…
Why not? This is how Unix/Linux desktops work already since at least the 1990’s.
So when you want to use Linux, why not work the Linux way?
It’s on the first screen of Desktop Behaviour - Workspace.
There is only “Show Informational Tips” option.
That is not true. I still have a machine running 13.2 and the desktop works with double click
If I use Thunderbird or Firefox or Kwrite and others they are all from LINUX and there are many points that work with double click and the simple click is only used to select and not execute
I think this confuses the user who does not know what will happen when clicking something
Must be a terrible experience. 
So just tell me that OpenSUSE will no longer offer this feature … so I go to any beach to see the sea and suffocate in the waves instead of looking for what does not exist 
It is not openSUSE in fact. It is the desktop (in your case KDE). And as many have told above, KDE basically supports it (I have no idea why). But apparently the descriptions what they see when clicking around on configuration screens differ from what you see. I assume that is the thing that should be solved (incompatible repositories used?).
And yes, it is difficult to discuss things happening in a GUI, because the discussion partners do not really see what happens at the other side. Which is why we always prefer the CLI for communicating on a forum like this. But that is not possible with the GUI :(.
But you should also understand that many people do not understand why something like a “double click” exists (except to the joy of doctors who care for RSI) and thus do not use it themselves. Nevertheless, in this thread they show how they care to help you by trying to switch themselves to it (and hope that they can undo it again).
As others have mentioned, that’s where you find the setting in Tumbleweed. But in Leap 15.0, it is in mouse settings (where the OP looked).
I’m not sure why it is not working for him.
Thanks for the answer
I should understand that the option in System Settings -> Input Devices -> Mouse the option single/double click does not refer to KDE
So I think I’d better get used to single click 