For administration, you have Group Policy, Active Directory, SAM, and various other things to read up on. Like others have said you can do everything in PowerShell but commands are super verbose. Microsoft does keep thorough documentation on it at least.
In terms of helping people with issues, you have the Windows Registry (kind of like dconf for GNOME), Backup Restore, Updates (most IT spend most of the time after fixing not working stuff, is convincing people to update their computers). If you can think on your feet, you'll be able to solve 90% of most workers' issues with some digging even if you didn't know Windows more than your average computer guy.
In terms of app development, tweaking and troubleshooting, there are a myriad of frameworks, like MFC, .NET, Electron, Microsoft Access databases somehow turned into a vital business application, etc.
Most app developers learn one of the various systems, then end up sticking with it causing Microsoft to support a hodge podge of 20+ year old native frameworks, while others import whatever newfangled crossplatform wrapper of the day is popular. So good luck if learning this is your goal.
The "next year" promise of the year...