You can change where sidebrain stores its data, by setting the variable
sidebrain-file-name.
You may want filenames to be usable on several machines (if, for
example, you keep your work on a fileserver or on removable media, which
may have different mount points on different hosts). To help with this,
you can set the hooks sidebrain-filename-save-hooks and
sidebrain-filename-load-hooks which should hold functions which
take a filename and, if they want to modify it, return the modified
version, otherwise return nil.
You can write code to put environment variables into the names on saving, and use
substitute-in-file-name to substitute the appropriate values on
the new host.
If you want to send sidebrain task lists by email, you may also want to use these hooks to make the names relative to a project directory.