Ionic 4.3, dubbed "Lithium Toast," introduces significant updates to the Toast component and addresses various bug fixes. The release enhances the Toast feature by allowing buttons for additional functionality, such as displaying text or icons and incorporating custom logic through handlers. Toasts can now include headers, providing more context for notifications. The update also improves the slider component with enhanced animations and resolves issues like incorrect tab navigation for Angular developers. These advancements, alongside other bug fixes involving datetime and input label design, aim to improve user experience and developer efficiency, with detailed documentation available for further guidance.