https://chrome.google.com/webstore/detail/onetab/chphlpgkkbo... (TL;DR click the button when you can't see the favicons anymore because you have so many open. It'll save them to a single page that includes all the previous tabs you've saved so you can cmd+f it if you REALLY want to find That One Thing You Had Open That One Time)
If you use that many tabs then you're better off using FireFox with the Tree Style Tabs extension [1]. Unlike the Chrome extension, it integrates properly with the browser window and you can hide the original tab strip.
[1] https://addons.mozilla.org/en-GB/firefox/addon/tree-style-ta...