For the record, i just thought i'd post this. I love Opera. I'm uninstalling it and cannot use it any longer. Since it will neither allow me to change the default string on supplied search engines, nor allow me to add my own and set it to default - i find opera unusable.
My particular scenario is as much aimed at google search. I can no longer deal with searches that return articles that are 8 years old .... and without noticing it you are working with obsolete information. I simply want to add a search string that limits it to the last year, so that i do not have to continually change the timeframe each and every time i search.
you can do this in chrome ... by adding your own search and setting it as default. Opera does not allow for this even though it has been requested forever.
bye bye opera ... i will miss you, for the most part.