With the Manage Designs toolbox, you have the option of opening one or more selected designs in their own design tabs.
Simply double-click to instantly open a design in the design window.
To open multiple designs simultaneously, hold down the Ctrl key as you select, and then click Open Selected.
Alternatively, click New From Selected. The only difference for practical purposes is that this command creates a copy which opens in a new design tab, thus preserving the original design file.
You can also open selected artwork by the same methods.
The Standard toolbar which is available at all times, also lets you open designs from the Design Library or any other network location.