Save your .sib files in a folder synced to Dropbox, iCloud, or Google Drive . This creates a "portable link" between your devices.
A way to put the entire Sibelius program on a USB stick to plug into any computer and start writing.
The "Sibelius Sounds" library can be upwards of 35GB. Running this over a USB 3.0 or even a USB-C connection can lead to significant lag and crashes.