Can you save an equation in mathcad prime 2.0, in a library so that you quickly can find it again?
Do you really mean "equations"?
Not sure what exactly you are after and how you would like to access your equations, but maybe it helps to know that you can reference one worksheet from within another.
Now Knovel (one former PTC partner - see in Matcad 15 the Tools menu) active develops an equation library.
See the picture please:
But sorry not only on the Mathcad platform . On the free ***** ****** platform too.