How can I customize the right click menu?

With macOS 10.13.6, I'm trying to change the menu item pointed out by the red arrow.

In TextEdit:

in Chrome

I tried the steps on a post, which is based on the existing services in Shortcuts, while my goal is to customize that item to "look up that selected words on the Cambridge Dictionary". Can someone help me on this?

If typical preference setting cannot do that, is it possible to do that by modifying system plist or by programming for it?

You can't change what the Context menu item does in so far that it is fixed to look up a word in the macOS dictionary.

You can't even change it to use a specific dictionary.

You can, however, make some changes. The look up that is done is according to the preferences of the Dictionary app and it is possible to change the dictionary used to another that Apple makes available, such as switching from British to American dictionaries.

To do this open the Dictionary app and select Preferences... in the 'Dictionary' menu and you will see a list of dictionaries that can be enabled or disabled as you wish.