The two "tabs" (OpenPGP Keys and OpenPGP Tasks) are not an intuitive method of change in functionality in Windows systems.
Windows uses a "ribbon bar" for that, where the tabs are located on top of the ribbon. The current location of the tabs suggest different output, not different functionality.
Since this product is a free cross-platform OpenPGP encryption tool, we were shooting for an approach that provided a consistent look-and-feel across all supported platforms. We do have users who are using our tool within their organizations of mixed systems. Using the ribbon is indeed more intuitive for windows users and we will look at implementing this in a future release of GoAnywhere OpenPGP Studio.