I have a folder with name "FOLDER".

In that folder PHP creates many folders dynamically. These folders has name with one only one character like:
FOLDER/A
FOLDER/B
FOLDER/C
FOLDER/D
...

I need to Disallow uploading of these folders.

PHPEd has possibility to disallow uploading (publishing) and as I see it has also "maks" option.
Can you help, ho to disallow uploading of these folders?

(I have only one folder in "FOLDERS" which needs can be uploaded (his name is "ALLOWED").)

PhpED does not appear to have the ability to disable the uploading of dynamically created folders based on a mask. You will need to tick the FOLDER for Do not publish, then the underlying folders will not be published.

If you do need files in FOLDER to be published, but not those dynamic folders, can you move those dynamics folders down a level? If you had FOLDER/CACHE/A, FOLDER/CACHE/B, etc. then you could mark CACHE for Do not publish and problem solved.