I think that it is way too easy to accidentally delete Note Files (right clicking a Note File from the File Menu), individual Notes in Note Files (left-clicking the red circle containing an X), and Close All Tabs (right clicking a resource tab) in L4. This is especially a concern with Note Files and (to a lesser extent) Notes, both of which may contain lots of valuable information not easy to reconstruct.
PROPOSED SOLUTION: When these "destroy-all" options are selected, there should be a Yes/No Popup Dialog that appears to users asking them "Are you sure you want to delete/close the Note File / Note / all tabs?" (appropriately worded for each situation). As a software developer, I almost always have added this "Are you sure...?" popup functionality to check with users in these kinds of situations.