Steps to reproduce: * Launch dolphin. * Open some plasma vault from the system tray. Expected behavior: vault should open in a new dolphin instance, like in earlier versions. Actual behavior: vault opens in the last-visited dolphin instance.
This is a new Dolphin behavior: now all externally-opened folders open in new tabs rather than new windows. If you don't like this behavior, you can change it in Dolphin settings > Startup > Uncheck "Open new folders in tabs"