Context menu event when multiple files are selected

When a file or folder in the Files pane is right clicked, a context menu appears. This event can be captured by using registerEvent(this.app.workspace.on("file-menu", delegate)).

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What I want to achieve is to add a menu item to the context menu whenever multiple items in the Files pane are selected using Alt+Click and the user right clicks. Currently, only two items are visible for me in this menu, “Move x items to…” and “Delete”.

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Unfortunately the file-menu event is not triggered in this scenario and I could not find anything related to this in the documentation. How can I capture this event, and the related information such as which files/folders were selected when the user right clicked?