Duplicate a list
Web & desktop app
To duplicate a list, click and drag the bullet point of the list and hold down Ctrl/Cmd at the same time. The label at your cursor will say "Copy 1 item".
Alternatively, Pro users can customize the "Duplicate current item" shortcut under Settings - Keymap - Working with lists. Pressing this shortcut will duplicate the current item you're on.
There's no way to duplicate a list on the mobile app right now.