In Windows 10, Libraries is moved down below in the File Explorer navigation pane. To bring it back to the top (as in Windows 8), here is a registry edit.
Move Libraries above “This PC”
Start Regedit.exe and go to the following key:
HKEY_CLASSES_ROOT\CLSID\{031E4825-7B94-4dc3-B131-E946B44C8DD5}
In the right pane, double-click the SortOrderIndex value.
By default it’s set to 84 (base: decimal). Changing it to 50 (or any value lower than the SortOrderIndex value assigned for “This PC”) should bring Libraries back to the top, vertically next to Quick access section.
To implement the same in Open / Save As dialogs in 32-bit applications, you need to make the changes under this registry key in addition.
HKEY_CLASSES_ROOT\Wow6432Node\CLSID\{031E4825-7B94-4dc3-B131-E946B44C8DD5}
Note: You may have to take ownership of the above key, and then assign permissions to your account before modifying it.
Applying as a Per-user Setting
If you want to apply the setting only for your user account, use this REG file instead. That way, you don’t have to change registry permissions etc.
Windows Registry Editor Version 5.00
;Move Libraries to the top of the navigation pane in Explorer
;For Windows 10 systems.
[HKEY_CURRENT_USER\SOFTWARE\Classes\CLSID\{031E4825-7B94-4dc3-B131-E946B44C8DD5}]
"SortOrderIndex"=dword:00000032
[HKEY_CURRENT_USER\SOFTWARE\Classes\Wow6432Node\CLSID\{031E4825-7B94-4dc3-B131-E946B44C8DD5}]
"SortOrderIndex"=dword:00000032
Copy the above lines to Notepad and save the file with .REG extension. Double-click the file to run it.
Libraries should be brought back to the top of the navigation pane, after Quick access.
Note that Libraries is hidden by default in File Explorer navigation pane. To show Libraries, right-click an empty area in the folder pane, and enable the “Show libraries” option.