How do I separate which game is installed on Steam based on windows user?
Solution 1:
Assuming you are using the same steam account across both windows logins, steam is what keeps track of what's installed on steam, not your windows account. There are however two ways to get something close.
Option 1 - Use steam's collections. Put all the games and software you are using into one collection and all the rest of your games in another one - that won't 100% hide them, but it will let you at least separate them.
Option 2 - Create a second steam account and use family sharing - You can share games and software you own with up to 5 other steam accounts now, if you create a second steam account, share your library with that other account, you can set what you do and don't want to allow the second account to be able to access - that way only what you share with that account will show up on steam at all. This list can be set up under settings>family>manage family view. This way your "work" windows login, will have a "work" steam account without access to the full library.
I haven't actually tried option 2 on the same PC, but you can log in and install games from multiple accounts onto one PC already, so it should work just fine. The only thing is you will need to sign out and into steam every time - steam isn't set up to have a saved log in connected to the user, just the computer as a whole.