Unlike in Chrome or Vivaldi, you just can’t press Ctrl+Shift+B and expect the bookmarks bar to appear in Opera browser even though it is Chromium/Blink based. If you use that shortcut, bookmarks manager will open, but not the bookmarks bar. Here is how to display the bookmarks bar below the address bar in Opera browser.
Showing bookmarks bar in Opera
I. Click on Opera menu > Bookmarks> select Show bookmarks bar.
Or
II. Visit Opera Settings (Alt+P), check ‘Show the bookmarks bar’ under ‘Bookmarks bar’.
Note: You need to follow either of the steps mentioned above to show or hide the bookmarks bar, no shortcut is available for you for this purpose.