you can share a dataset by clicking on it in the flow, and then in the right top corner click the 'share' icon. You can then choose the target projects from a drop-down menu.
You can also do it programmatically from the project where your original dataset is in.
client = dataiku.api_client()
project = client.get_default_project()
settings = project.get_settings()
settings.add_exposed_object('DATASET', 'your_Dataset_name', 'your_target_projectkey')
you can add extra target projects by the same code.
As far as I am aware, you can not change the reference settings from within the project the dataset is shared in, except from deleting it in the flow.
Hope this helps!