How to modify frappe to increase the number of column for the child table in the doc

Hi, All
I am beginner and started to explore the details of ERPNext which is amazing. I have a use case which require more column in the quotation items in the quotation form. The user need more information presented in the screen to complete the pricing of the item.
I have already used up the 10 column and the other 2 was occupied by the system itself.
I searched the forum and realized that it is a limitation so far.
But just want to check if I want to modify the core to overcome this limitation, is there a rough idea how to achieve it? I am not a very experienced front end developer, but experienced more in the backend.
Any suggestion or ideas how to achieve it will help me modify js/css by myself to achieve it.
Thanks a lot.