It seems like we currently do not support ~ in our config, e.g.

import mne

mne.set_config("MNE_DATA", "~/Data")
mne.datasets.sample.data_path()

raises a FileNotFoundError: Download location ~/Data as specified by MNE_DATA does not exist. Either create this directory manually and try again, or set MNE_DATA to an existing directory. (the directory exists).

Is there a reason why we would not want to expand the tilde? This would be useful to store MNE data in the same location within a user's home directory across operating systems.