How to set primary display?

I know I’m bad at find things, but every tutorial on the internet points me to here and claim that there should be a checkbox to desinate a primary display. The truth is there is none.

I also tried to find the settings everywhere in the System Settings, even in the YaST, nothing was found.

What do you mean by primary display? How’s that different from the others? Which desktop environment / display manager / graphics driver?

I posted the same thread on reddit with the screenshot.

By primary display I mean when something launches, it should launch on the main display instead of randomly choose one or on the secondary display. There is another reddit user replied my thread with his settings, he/she’s setting have one more chechbox than mine, which is Primary display.

I’m using KDE with kwin, and the stock amdgpu driver.

That checkbox is useless AFAICT.

Find the Window Behavior tool, activate the Advanced tab, and find an option for Window placement that fits best for your use case. For me “Under mouse” almost works, except on startup since the cursor is between both monitors, but slightly to the right. But to remedy I just use Super+ArrowLeft to reposition the window. My advice: don’t spend too much time fighting with it.