While in Admin account on Win 10, creating a tutorial project, you can not save in the temp folder. If you are using Standard User account, everything is fine.

To reproduce:
1. Sign in in to admin account
2. Open unity
3. Open Learn tab and select 2DRoguelike tutorial
4. Press start
5. Try to save the scene
6. Observe as the prompt asks you to save in the Asset folder when you all ready are in there
7. Sign in in to Standard User account
8. Repeat 2 - 5 steps
9. Observe as you can save the scene without any problems

Reproduced on: 5.6.1f1 5.6.1p4 2017.1.0b10 2017.2.0a4

Windows 10 Pro