This feature Controlled Folder Access only works when Windows Defender Antivirus is your main security software; if you're running third-party antivirus on your machine, this feature won't be available. Controlled Folder Access Wont be available when you use another antivirus program I found a link here that may help explain it more if Okay to post it https://m.windowscentral.com/whats-new-windows-defender-security-center-windows-10-fall-creators-update