I ll write this as an answer even though it is given in the comment (thanks @acl) as this is going to be a life changer for me.
The solution is
Right (or on a mac control) click on the item and it will give you the option to open a new window.
For instance, let's assume one is looking at this tutorial
and you want to visit the page Solve a Differential-Algebraic equation and keep the howto page open.
So you have
After one right clicks
Select open in new window et...
I have been frustrated about what I thought was this missing feature for years!
Thanks again StackExchange!
As a side note, I also did not realize that the frontend allows you to open more than once the documentation center.