Where is that button?  I don't recall seeing it and don't see it now.

I think if you're not seeing it there must be something else amiss. When you click the standard 'Networks' popup in the system tray, underneath the word 'Networks' at the top of the popup I have a check box with a wifi symbol next to it. Next to that there's another one for airplane mode, and then a Hotspot button. All on Leap 15.4.

Otherwise, in the list of wifi connections in System Settings, if you click on one, then look under the 'Wi-Fi' tab on the right pane, you don't by any chance have the Visibility check box ticked, making it a hidden network? Obviously you wouldn't have done that deliberately but maybe the config has somehow become corrupted.