I am not sure what that looks like, but I did find some add ons that enhance Tab Groups. *[https://addons.mozilla.org/en-US/firefox/addon/tab-groups-helper/?src=search] *[https://addons.mozilla.org/en-US/firefox/addon/tabgroups-menu/?src=search] *[https://addons.mozilla.org/en-US/firefox/addon/tab-mix-plus/?src=search] Was there an add on that did this that is not longer compatible with version 35? If so, to get it back you will have to download it and reinstall the older version of Firefox, which I do not recommend for security purposes.

Thank for the response, I already figured out why this happens it's because i have so many tabs open...& it doesn't fit so Mezilla makes it into a stack instead of side by side. Thanks for taking the time to answer my question!