How to edit table section of quotation?

Change item code to item name
Add description column
Add Brand column
Add Size Column

customize doctype → find this table and make changes,3 additions can be done, not sure about that field rename though

When i try to edit the table.

frappe doesnt allow changing standard fields on core doctypes, you can add the rest 3 fields, but wont be able to change this, if you are keen on changing that, you can turn on developer mode and edit the doctype which is not recommended, and will cause issues when updating

Thank you for your response
Also when I add brand It doesn’t show on the quotation table
(I have also reloaded)

tick 'in grid view" for that