The Flywheel data hierarchy requires that every session be part of one subject and every subject be part of one project. Therefore, metadata on the subject tab in the session view is linked between all of the sessions with the same Subject Label. When changes are made on the subject metadata tab they are propagated to all of the subject's sessions simultaneously upon saving.
This comes into play when moving sessions to a new project. If there is not a subject with that session's Subject Label already in that project, the session can be moved without incident using the `Move Session to Project` from the Action menu.
In the background, a new subject with that Subject Label is created in that project, and that session is assigned to that Subject in the Flywheel hierarchy.
However, if that Subject does exist, any conflicts between the subject's metadata will need to be resolved. The metadata will be merged if two fields are identical or the field is empty on either subject. If different values exist in the same field, then the one that will be used will be for the most recent session according to their timestamp.
This is accomplished using the `Move Sessions to Subject` action. That will bring a modal up to select the project the subject is in.
You are then prompted to either create a new subject or choose an existing subject. If it is a new subject, then you can enter new Subject Label and proceed. If it's an existing subject, you will be given a dropdown list of subjects to choose from.
Finally, after clicking save you will receive a confirmation modal that shows if your session move was successful.