Opera opens a new window when opening flow or WhatsApp in sidebar

[A Former User]

A Former User last edited by A Former User

This happens on Kubuntu 18.04

https://imgur.com/smmuhMd , flow is closed
https://imgur.com/I1BpF4G , flow is open

On Kubuntu 17.10 this did not happen, so it's probably caused by KWin (KDE's Window Manager) or the plasmashell, but I'm not sure. The newly spawned window also doesn't use the POP icons I applied, instead using the stock Opera icon. When closing the sidebar 'app' said window disappears. If I click on the window icon, the sidebar 'app' closes.
I hope you can fix that