The Firefox URL bar currently allows you to search through tabs. A shortcut to do this is through the % symbol in the navigation bar. I have a few suggestions to improve this feature.
Active Media & Inactive Media
Display results with either playing content or paused content through the terms 'playing', 'paused' or 'media' for both
Display media status in the results
Currently the tab search result list doesn't display if the tab has active or inactive media
Covering all Firefox instances
This might not be possible or desirable but it would be nice if you can search through all container accounts or a private session. It was a source of confusion for me as to why my tab searches resulted in nothing