First install Tree Style Tab plugin.
Now for the tab hiding part:
- Go to your profile directory, directory's path can be found by going to about:support and open the Profile Directory
- Create a directory called
chrome
- Create a file called
userChrome.css
- Put these in the file
#TabsToolbar
{
visibility: collapse;
}
- Go to about:config and set
toolkit.legacyUserProfileCustomizations.stylesheets
to true
- Restart Firefox to see the changes