2FA Pro is one of the best desktop application to store all of your 2FA TOTP keys!
It works fully offline and protects your privacy - it does not connect to the Internet in any way and does not have any telemetry.
Can run in system tray, available at all time on your taskbar.
It was made to be partially compatible with the Authenticator Pro - open source Android application, providing similar 2FA solution. You can export or import Authenticator Pro backup, although my application will use only TOTP keys, while ignoring all others.
Application is actively being developed by me and you can expect new updates every now and then.