Be careful with old versions!
These versions are displayed for reference and testing purposes. You should always use the latest version of an add-on.
Defaults keys are :
Shift+1 : Open previous link into current tab
Shift+2 : Open next link into current tab
Shift+3 : Open previous link into a new tab
Shift+4 : Open next link into a new tab
These shortcuts are customizable using the Options Dialog