How to start with an empty session in KDE
KDE will automatically start from where the user left off in their previous session. KDE, for example, keeps track of open applications and their window positioning when a user logs out and will open such applications when the user logs back in.
It could be useful to some, while others wish to start from a clean slate. You can configure KDE to start from an empty session for your user from the System Settings.
Steps to configure session startup option for KDE:
Open System Settings from launcher.
Click on Startup and Shutdown menu on the sidebar.
Go to Desktop Session panel by clicking on the sidebar menu.
Click on Start on an empty session radio button in the When logging in section to start KDE with an empty session.
Click on the Apply button to save the configuration change.