Can I copy PS4 game save data from old user to a new user?

It appears that it is not possible to transfer saves between users:

Save Data is account locked so you cannot transfer save data to different accounts. basically to prevent cheating, boosting, etc on the trophies. among other reasons. mainly Piracy

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You can only transfer them between different PS4 systems, though without the same user on the new system, they cannot be accessed (for the above reason):

As a backup, you can copy saved data to a USB storage device connected to your PS4™ system. Copy saved data from the USB storage device to another PS4™ system to continue playing a game. For each game, you can select the saved data to copy.

• To use this feature, you need to have signed in to PlayStation™Network at least once.
• FAT and exFAT formatted USB storage devices are supported.
• Be sure to fully insert the USB storage device into the USB port. Some devices are not compatible due to shape or design.

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