Oh, yes, this program does not support Godot 3 Encryption yet. So you can use it to open and unpack files, but they will remain encrypted.
This program, as I understand, it only works with Godot 3. Because it could not get the key from my Godot 4.0.2 test program.
But I like the idea of this program and I thought I would do a scan of the assembler of the program myself. But then I decided that it would be more difficult and I have already made my own program that iterates through all the bytes of the engine in search of the key. It is much slower (2-6 minutes), but thanks to this program I have greatly optimized GodotPCKExplorer.
Later, I may implement a key search in the assembler of the program.