SNiFF+ handles file sharing among working environments by requiring that all affected working environments have the same project directory structure. This is not a restriction, but rather the easiest way for file sharing to work. A SNiFF+ project's Project Description File stores, among other things, structural information about the project -- information such as the names of project files and their location relative to the project directory, and the names and locations of any subprojects. When all working environments that share files have the same project directory structure, SNiFF+ can easily find any project files or subprojects.
The project directory structure of the Shared Source Working Environment (SSWE) is the basis for all other working environment project directory structures. SNiFF+ automatically copies the SSWE's project directory structure into your other working environments for you. Note that SNiFF+ only copies the SSWE's directory structure -- and not contents.
The following diagram illustrates the idea of equivalent project directory structures: