EndNote can be shared using the Compressed Library feature. In EndNote, go to File, and click Compressed Library. There is a good explanation of it starting on page 107 in the EndNote manual that is installed on your computer.
When sharing manuscript development, one person could offer to do all the references. The collaborators can manually mark in the text where a reference should be placed. The designated person can accumulate the references in EndNote as we go along. When the manuscript is done, use EndNote to insert all the references.
IUSM Librarians have found that most joint writing projects benefit from use of the Microsoft Word feature, Track Changes. It is our experience that Track Changes and EndNote do not work well together.
A common mistake that we see with use of EndNote by joint writers is that not all joint writers properly fix and remove citations and references that have been inserted by EndNote. Someone may use the keyboard Delete key on an EndNote citation or reference, which can leave EndNote field code in the document and corrupt the document. A corrupted document can be serious and unfixable. We know because we get the phone call as to what is wrong with EndNote. In this case it is operator error. If several are going to use EndNote on the manuscript, then we suggest that upfront, everyone knows to use the EndNote Edit Citation feature to remove a citation and fix it.
We recommend that one person be in charge of the references. At the end of the writing and after Word Track Changes is turned off, use EndNote to insert the citations and references.