The share function is one of my favorite features, as I can get a barcode of the tracking code. Our post office can read the barcode very quickly. However, it is a bit slow to access the feature for multiple packages as it requires 3 button presses.
On the detailed view of a package, add a share button next to menu, completed and refresh button. The share button can remember the last action (message, qr-code, barcode) like chrome and firefox do.