If you would like to change this setting you should apply some registry changes.
Here it is relative workflow:
- start --> regedit
- Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- (be aware to check this section too) HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- You should Right-click Advanced folder and choose New > DWORD (32-bit) Value. Name the new value JumpListItems_Maximum
- Double-click JumpListItems_Maximum value to open its properties window.
- You should put a value between 15 and 20.
[update 2020.04.29]
Please review below article if you like to increase jump list show items:
Windows 10 - How to increase Jump list items number