Expanding "options" in select field

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1

Hi
Trying to do some custoization on a “Select” field. e.g. when I add anothe roption ( Option-3) , then the additional option is displayed in the field drop-down, but when I save the doc, it still only allows the first two options.

frappe.ui.form.on('DOCTYPE', {
    refresh(frm) {
        // your code here
        // your code here
        let fields="\nOption-1\nOption-2\nOption-3";
        frm.set_df_property('linked_doctype', 'options', fields);
    }
})

And there are not “validate” methods that is enforcing this. Is this inherent to the
Frappe Framework ?