There is an easy way to add any search to your Opera browser.
For example if you want to add free wordtracker keyword search to your Opera then do the next steps.

1. Go to Free Keyword Suggestion Tool from Wordtracker

2. Right click on their search bar

3. Click on Create Search

4. Click on details

5. Assign letter "k" for shortcut.

6. Click OK

Now when you need to check some keyword you only need to type
in your address bar

k my keyword

and press enter, your search will be executed right away with the wordtracker results for my keyword .

You can add on this way any search to your Opera.

For example I use k for keyword tracker, and d for domainsbot domainname suggestion tool.