go2back.tumblr.bookmarklet

javascript:
(function(){
  var id=Number(window.location.pathname.match(/\d+/)[0]);
  url='http://www.tumblr.com/dashboard/1000/'+(id+1)+'?back';
  window.open(url);
}
)();

offset 対応版

javascript:
(function(){
  var id=Number(window.location.pathname.match(/\d+/)[0]);
  url='http://www.tumblr.com/dashboard?offset='+(id+1);
  window.open(url);
}
)();