Is there a Node Reference URL Widget module for entity references? I just learned that there is the nice Node Reference URL Widget module.  Basically, it allows you to add a add a A link in the node view pages of content type B, if there is a node reference A->B.  When you are viewing a B node, clicking on the add a A link would lead you to the node creation page of content type A, with the A->B field populated with the B node you were just viewing.  That way the user do not need to figure out "which node B am I adding this node A to?"

Our sites mainly use Entity Reference.  Is there a module that provides similar functionality for entity references?
OK.  I see there is Entityreference prepopulate.


  Allow prepopulating any Entity reference field via URL


Going to try it now.