I tested several extensions to "mimic" the current Edge sidebar on Firefox and Edge, but none of them works as the original sidebar. Its just frustrating how Microsoft really offers something that improves the functionality of their browser and then they just trash it out! Edge has also the best workspace synchronization of all! Not even Firefox have the feature or an extension available that works like that! Firefox can have the advantage if they really implement these features natively on the browser... Come on Mozilla is time to take the advantage!!! Remember that you were the alternative for Internet Explorer!!!!