I don't want to be like other extensions and put some extra element in the current tab just so the user can see what the extension wants them to see.

I want to do it directly from the sidebar or popup, when a contextMenu is clicked.

I already looked this up specifically for popups, and found out that It may be triggered using a keyboard shortcut, so... do extensions have a way of falsely pressing keys?

Google shows no trace of programmatically opening an Opera extension's sidebar. though, the sidebar is the main extension piece