All QuickLinks sent from your account live in the QuickLink panel on the left side menu.
Select the Edit icon from the QuickLink Panel:
This will open the QuickLink Wizard, where you can make necessary changes to settings, including removing or adding new files and recipients. Hit "Save" and the QuickLink will update immediately.
Drag and drop new files over the QuickLink:
Select the Grid Icon to re-order or remove files from the QuickLink
Be sure to hit "Save" after making any changes in the QuickLink Wizard for your updates to be remembered.