Following the release of Cyber's PS4 Save Editor and the leaked source code, today soad08 shared a guide on how to edit PS4 game saves with the Cyber Save Editor without knowing Japanese for those who didn't update to PS4 v4.50 OFW which currently blocks it although there is a Bypass Tutorial. 
To quote: Cyber Save Editor Tutorial
It seems that only Japanese saves are supported at the moment, so don't get it if you use US or EU saves!!!!
ALWAYS BACKUP YOUR SAVE BEFORE DOING ANY OF THE FOLLOWING STEPS!!!!
For a list with all compatible games click HERE.
Step 1: Copy the savegame you want to mod from your PS4 to flash drive and put the flash drive in your computer.
Step 2: Click in the top left side to show which saves are available.
Step 3: Double click your save and choose which mod you want (Upper red circle) , then click on apply (red circle below)
Step 4: The editor asks you if you are sure to apply this mods, click yes (red circle, here it says "ja" because my windows is in German)
Step 5: Wait until the editor applied your chosen mods.
Step 6: Put your flash drive back into your PS4 and copy your save onto your PS4.
Step 7: Launch game and enjoy!
FAQ:
How can I get Japanese games?
You can create a Japanese account and download games there or visit Play-Asia.com (here you get also PSN cards for Japanese store).
If I mod a savegame I always get some message on Japanese, what does it mean?
This message means that the server is not responding, i got it all day today, i dont know any workaround, at the moment only suggest i can make is to try it later again.
Cheers to @HydrogenNGU for the heads-up on Twitter earlier today!
To quote: Cyber Save Editor Tutorial
It seems that only Japanese saves are supported at the moment, so don't get it if you use US or EU saves!!!!
ALWAYS BACKUP YOUR SAVE BEFORE DOING ANY OF THE FOLLOWING STEPS!!!!
For a list with all compatible games click HERE.
Step 1: Copy the savegame you want to mod from your PS4 to flash drive and put the flash drive in your computer.
Step 2: Click in the top left side to show which saves are available.
Step 3: Double click your save and choose which mod you want (Upper red circle) , then click on apply (red circle below)
Step 4: The editor asks you if you are sure to apply this mods, click yes (red circle, here it says "ja" because my windows is in German)
Step 5: Wait until the editor applied your chosen mods.
Step 6: Put your flash drive back into your PS4 and copy your save onto your PS4.
Step 7: Launch game and enjoy!
FAQ:
How can I get Japanese games?
You can create a Japanese account and download games there or visit Play-Asia.com (here you get also PSN cards for Japanese store).
If I mod a savegame I always get some message on Japanese, what does it mean?
This message means that the server is not responding, i got it all day today, i dont know any workaround, at the moment only suggest i can make is to try it later again.
Cheers to @HydrogenNGU for the heads-up on Twitter earlier today!