It's unlikely that there will be a Windows version of the app anytime soon, unfortunately. Gospel Library is the only member-facing app developed by the Church for Windows (Windows 8.1/10), and it's a volunteer project – so resources are very limited. LDS Tools for Windows did exist, but it was recently removed from the Windows Store because there weren't enough resources to update it to current standards.
Windows has a large user base, but most of that user base is in the desktop/laptop computer space, not the mobile space (which is small compared to Android and iOS). The Church hasn't shown a lot of interest in developing apps for desktop computers, because desktop computers are more likely to have consistent internet access, which allows people to access resources directly at LDS.org.
Samuel Bradshaw • If you desire to serve God, you are called to the work.