Sorry, Steeven, but there is no such option that I can find. Security and Privacy has four sub-menus: General, FileVault, Firewall, and Privacy. Under which would you expect to find the solution you propsed?
See also this thread, which seems to indicate the only way is to bypass Apple’s security mechanisms:
https://community.brave.com/t/installing-brave-on-macos-beta-6/75529
[UPDATE] . I figured it out. You need to go to System Preferences directly after you try to open the app. All set now.