anyone had a success in adding a custom column/sublist via script and inserting it in-front of another column field? I tried the commented part below. Thanks in advance! (insertField works on header though)

var sublist = form.getSublist({
	id: 'item'
});
var customTextField = sublist.addField({
	id: 'custpage_text_field',
	type: serverWidget.FieldType.TEXT,
	label: 'Text Field'
});

/*
form.insertField({
	field: customColumnField,
	nextfield: 'quantity'
});
*/

If you manage to find this (documented or otherwise) please post back to this thread. Searching for this myself

You would probably save yourself some time adding the column in the usual fashion then scripting to show / hide it with a user event, although i don't know your exact use case.