By default, the linkto tag will open the link destination in the current tab of your browser. In order to open it in a new tab, we can use the attribute new_tab and set it to true:
{% linkto "http://example.com (http://example.com/)" new_tab:true %}label{% endlinkto %}
Please note that you cannot pass a variable to new_tab; it needs to be true or omitted altogether.