Bonjour and thanks for the feedback! There's a surprising amount of complexity in decomposing symbols back to their parent (aside from undo operations), and I'm not sure we could ever do a great job for this feature unfortunately. Symbols having their own timelines raise plenty of questions on what expected behavior would be for their animations, especially on different timelines - should they be merged or joined? I'm not sure there's a great answer.
The best workaround right now is to enter a symbol, copy the elements, and then paste with animations onto the parent.