Anyone knows how to delete a saving slot?

You wil have to delete it from the memory card. Don't putt the came in the player and you will be have to klikk one brows to get to memory card hven you do that you can delete anything you like

Well if it for you're pc then go into the folder were you put you're install files click on final fantasy folder in ther should be all the files then there should also be another folder in there saying final fantasy vii click on that then go to the save folder there you will find all you're save files delete the one that you don't wont making sure you don't delete the one you wont to keep though lol hope that help if you playing it on pc

JUst Save THe game in the save slot that you wanna be deleted
...

This is PS4 VERSION

Tried to find in-game for a delete option. There is no option in the PS4 version. I looked in the Saved Data Management and there is only 1 FF7 save file. I could not delete within it. If I delete that then ALL my save slots in that save file will get deleted. I really don't want 4 saves slots in 1 file.

Solution for PS4 version deleting save slots (I still think there should be an in-game delete option).
Here's what you should do:

Go to game
Go to Continue?
Select which save slot
While in game, save to Save 2
Press Touchpad
Press Options button
Select Close Application
Press Up on the D-Pad
Go to Settings
Go to Application Saved Data Management
Go to Saved Data in System Storage
Go to Delete
Go to FINAL FANTASY VII
Now there should be 2 save files (it would say something like, "FINAL FANTASY VII 3/3/2020 7:11 AM 7.5 MB Save 1" and "FINAL FANTASY VII 3/5/2020 10:09 AM 10.49 MB Save 2")
Delete Save file 1
Done

And if you want, you can transfer you're save slot to save file 1. U just gotta go back in the game, save it there, go to save management and delete Save 2.