Windows 10 by default displays 12 items in the Taskbar Jump Lists. In Windows 7 you could change this number via Taskbar and Start Menu Properties, Now this is no longer possible.
Increase number of Jump List items in Windows 10
If you want to change or increase the number of Jump List items in Windows 10, you will have to make use of the Registry Editor.
Open Registry Editor and navigate to the following key:
Right-click Advanced > New > DWORD (32-bit) Value.
Name it JumpListItems_Maximum
Now double-click on it and change its Value data to the number of items you want to be displayed – say 20.
Restart Explorer and you are all set!