How to do it properly, and then you don’t have to redownload 31gb the game files.
Steps
1. First, you must update Apex Legends origin version to the latest version.
2. After that, rename the game folder
origin version from Apex to Apex Legends (In my case, be like that)
3. After that, Move the game folder to the installation directory (SteamLibrary/steamapps/common)
4. Then install via steam, steam automatically discover the existing game files.
5. That’s it, you good to go.
Credit to Ching-Cheng-Hanji
Apex Legends is the award-winning, free-to-play Battle Royale team shooter from Respawn Entertainment. it is available on Steam now. you can get the game from the steam store.