５はfoxy gestureにこれ登録したら？

var selectionDOM = window.getSelection().getRangeAt(0).cloneContents(),
links = selectionDOM.querySelectorAll('a'), hrefs = [], i;
for(i=0; i<links.length; i++){
hrefs.push(links[i].href);
}
hrefs = Array.from(new Set(hrefs));
for(i=0; i<hrefs.length; i++){
var href = hrefs[i];
if (href && href.match(/^(http|file)/i)) {
executeInBackground((href,i) => {
getActiveTab(tab => browser.tabs.create({
url: href,
index: tab.index + 1 + i,
active: false
}));
}, [ href, i ]);
}
}