Within Notes and Expeditor, it's possible to set the Windows and Themes -> Open each document in its own tab preference to ensure that newly opened perspectives do so in the client UI. This is the default "tabbed" behavior you're likely well familiar with.
Even with this set, it's possible for some perspectives to open within a new window. This behavior might be non-obvious given the aforementioned preference. Ensure that the "Always Open in New Window" context menu item is not checked by right mouse clicking the item in the launcher (Open menu). If it is checked, this will - well - always open the launcher item in a new window.