Good day @yashprabhugaonker ,
The best solution in this case is to create a custom filter based on excelFilter / serverExcelFilter. For this you can use webix.extend and change logic of filter’s render method a bit (here you need to leave all the functions of the old method, just add a new event handler).
In your example, there is a pop up with a filter inside it. So, you could add an onShow event handler to the pop up and when it is shown you could get the input and set focus to it.
Check the snippet: Code Snippet .