As of the final update of FIFA 23 (Title Update 18), there is no public standalone encryption key you can paste into an old version of FET. However, functional editing is possible.
To edit FIFA 23 today:
If you are stuck, you are likely facing one of these three issues: fifa editor tool encryption key fifa 23
Even after decryption, the file is compressed using EA’s proprietary Chunklzx compression. The FIFA Editor Tool will automatically decompress it. You will see a progress bar. If it freezes, your key is wrong for your Title Update version. As of the final update of FIFA 23