browserSettings.openUrlbarResultsInNewTabs

A BrowserSetting object whose underlying value is a boolean.

When the user focuses the address bar and starts typing, the browser offers autocomplete suggestions: a dropdown list of web pages based on the user's incomplete input and their browsing history.

If set to true, then when the user selects one of these items, the item is opened in a new tab. If set to false (the default) the item is opened in the current tab.

function logResult(result) {
  console.log(`Setting was modified: ${result}`);
}

browser.browserSettings.openUrlbarResultsInNewTabs
  .set({ value: true })
  .then(logResult);