Embedding tools helpers in Opera is very simple, despite the fact that there is no API for creating plugins.
For example, you need a password generator. there are two approaches, one using an app server (apache + php is quite suitable for this role), the second with javascript.
In the case of an appserver, we write the script in our favorite programming language as usual. There are no special requirements - output yourself html as usual. Here is the script that I got (
link 1 ,
link 2 ). After writing the script / servlet / program, go through HTTP to your page and drag and drop dragging the URL icon from the address bar to the sidebar. If everything is done correctly, an icon will appear on the panel. Click on the icon - see the result.

In the case of javascript, everything is almost identical, except for a few moments. (no server is needed for this case, this option is autonomous)
Open
paste.org.ru/?t4t9to (
link 2 ) and take the whole javascript code (starting with javascript, ending with the last;). Open a
new tab, and paste this code into the address bar, go to. Now, in the same way as indicated earlier, drag the icon in the address bar to the side panel. By default, the name for this tab is opaque. Right-click on the tab-> change panel-> name, change it to harmonious.

Of course, this is not my discovery, and not even an innovation, it just thought that there are some people who do not know this. The example with the password generator is selected as the easiest, but useful (he himself did so only to quickly select a password for new mysql users)