Packages can be reshaped through the Inventory view. You can transfer inventory off a package or onto a package.
To reshape a package, navigate to the Inventory view. You will want to open the Transfer Inventory blade. This can be done by selecting the action menu at the top right of the Inventory heading, or by selecting the action menu of the product you are transferring.
From the transfer inventory blade, transfer the inventory onto a new or existing package by selecting the Destination Package.
The Transfer Inventory blade