You can only use custom scripts. It is now working on ERPNext Cloud with some paid assistance. 
Hello @creamdory and @JoEz
I was able to set the query by calling the whitelist method in .py and the returned value is correct. But I am facing another problem: when clicking on the field and listing the values, so I usually start type the first and second character to reach for the required selection, but the problem it is not filtering and returning the values that start by these typed characters.
But, if I only set filter at .js file without calling the method to return the query, the values are filtered based on the entered characters.
What is the solution for this? Because if the values are not returned based on the entered characters, then it will be very hard to scroll down and looking for the needed value … not practical way.
I am sure there is something need to be set in the query so it will enable this feature.
Regards
Bilal