Hi,
There's not such certain permission we can define.
If the user creates a folder, they are the owner of that folder, so they can do whatever they want with that folder. Try these permissions out
Please apply these settings onto: This folder, subfolders and files
Traverse Folder/Execute File
List Folder/Read Data
Create Files/Write Data
Create Folders/Append Data
What you should get out of this is the user cannot move/delete existing files and folders, but any file or folder they create they will have full modify permissions. I have tested this and that's what happens. I am not assuming anything by reading text,
these are what works. You can modify from this to get where you want to be.