hi @augusto !
First idea I've in mind is to always keep an empty line at the end of your table and set each row of it (or only those you want the user can fill) as editable.
When you create your line in JS, just add an event launched when you want (for example : when 1 row is filled, when all of them are filled, whatever you want)
If number of line is a problem, juste use a navigation to your table (i.e 25, 50 or 100 entries per page) and add dynamically the editable row at the end (no matter on the page index you are)
I think this is the best for the user!
Maybe not regarding performance but, honnestly, the process is not so heavy
And for bootstrap integration, no probleme, your table keep the bootstrap style
But if you really want a modal dialog to create new line (which is very heavy when user needs to add many line I think), take a look at Bootbox, personnaly I really like it and it is very simple to use