Hi @jinsy,
Please apply it.
frappe.ui.form.on("Leave Application", "refresh", function(frm) {
frm.add_custom_button(__("Approve"), function(){
frm.set_value('status',"Approved");
frm.refresh_field('status');
frm.save('Submit');
}).addClass("btn-success").removeClass("btn-default");
frm.add_custom_button(__("Reject"), function(){
frm.set_value('status',"Rejected");
frm.refresh_field('status');
frm.save('Submit');
}).addClass("btn-danger").removeClass("btn-default");
});
Then Reload and check it, please.
Thank You!