Moving folders · Moving from What's Using Space
Why is there no Move to fast drive button on some folders in What's Using Space?
Short answer: Move to fast drive only appears on ACTIONABLE rows big enough to be worth moving. Other rows are informational (like Applications or the Photos library) or deliberately left alone. Use the Apps window or Data Parking for those.
The button only appears on rows marked ACTIONABLE that are big enough to be worth moving. Other rows are there to inform you — for example your Applications folder, Photos library or Mail library — or are areas Storage Studio deliberately leaves alone, such as browser profiles and data apps need to keep you signed in.
If a row is informational, you still have options: apps can be moved from the Apps window, and any ordinary folder you choose can be moved with Data Parking.
See What is Data Parking? and Why won't Storage Studio move my browser's folder?