You may need a tool like the AC Save Tool to change the Save ID so the game recognizes it.
A official "feature" exists that allows you to bypass the grind if you are around Level 30 and want to access late-game content immediately. Level 45 Boost : If you own The Curse of the Pharaohs
From behind a dune, his steed, a majestic black stallion named Silver Fire, galloped toward him. But Bayek didn't mount up. He stood his ground as three heavily armored brutes charged him.
: Frequently lists level-specific saves, such as Level 39 or Level 30 presets . Installation Guide for PC
C:\Program Files (x86)\Ubisoft\Ubisoft Game Launcher\savegames\[Account ID]\3539 .
You cannot simply drag a CODEX save into your Uplay folder; the encryption is different.