Arrange tabs in Safari on Mac
You can rearrange tabs for convenience and pin frequently visited websites for easy access.
In the Safari app on your Mac, do any of the following:
Rearrange tabs: Drag a tab to a new position.
Pin a website: Drag the tab with the website you want to pin to the left side of the tab bar. See Pin frequently visited websites.
Scroll through tabs: If there are more tabs than are visible in the tab bar, swipe left or right over the tab bar to scroll through your tabs.
You can also press Command-1 through Command-9 to select one of your first nine tabs. To allow this, choose Safari > Preferences, click Tabs, then turn on the option. See Change Tabs preferences.
Show tab overview: To see thumbnails of all your open tabs, click the “Show tab overview” button
, or pinch closed on a trackpad. To view one of the pages full size, click its thumbnail. To close a tab, click the Close button 
in the upper-left corner of the thumbnail.Convert all Safari windows to tabs in a single window: Choose Window > Merge All Windows.