A way to set templates for responsive breakpoints so that one can quickly apply the breakpoints between pages and designs would be great, rather than redoing it every time - unless there's a trick that I've missed.
Not sure if this is what you meant but you can...
a) create a rectangle.
b) create the breakpoints you need.
c) right-click on the rectangle and select "Add to library'.
d) name the object in the library so you know what the bpts are (e.g. BP-480-768-960)
e) on your new page/site, drag the rectangle out of the library by click-holding the breakpoint icon on the right of its name.
f) place it on the page.
g) delete the rectangle (the breakpoints will remain). Note: if you just drag the library object by the name, it doesn't bring the bpts over with it.
The best option there is right now is to clone pages to make the new ones