Is there a way to always open bookmarks in a new tab in Opera?
You can have it so that all bookmarks open up in new tabs by setting it in your preferences:
Tools > Preferences > Advanced > Tabs
Or Ctrl + F12
Then uncheck Reuse current tab.
To be double sure, click on Additional tab options....
Make sure that Open windows instead of tabs is also unchecked.
Click OK to save the changes.
Now, when you open a bookmark, or a favourite from the Personal Bar, it will open up in a new tab.