Here's how to switch between the Google accounts you use with Gemini Notebook, formerly NotebookLM, in Kortex. Click the Kortex icon in the toolbar to open the side panel. Then click Dashboard in the panel's header to open the Kortex Workspace.
At the bottom of the sidebar you see your email. If you use more than one Google account, Notebooks from is there too. Open Notebooks from and choose the account.
Each one shows its email, and the default one is marked. Kortex shows Switching account. Then it says Showing notebooks from, and the email.
The Notebooks, Sources and Artifacts tables now show that account only. With more than one account, the side panel's header shows your Gemini Notebook account. Its Notebooks tab lists the notebooks of the account you picked.
Find the full steps and fixes on the Kortex website.