Don't make a separate topic on a update, your better off replying on a previous or different topics, and no, self-dedicated updates/shout out topics isn't allowed you plug-in.
Few exception is being is on a W.I.P moc, if it take about over a week to make, you can't continuously spam unnecessary structure topic update, so your better off continue replying on the same topic. But you can make a separate topic if the final product is complete, a newer version with noticeable adjustment can also have a separate topic if the moc appearance to have effort put in.