I just had the confirmation from Mentor that it is not supported exactly the way I was looking for. Here below the answer that I received:
Basically, at this time, IPC356 isn't available in PADS Pro Layout product. If you use the Output > ODB++, ODB++ includes an embedded netlist. You can export IPC-2581 from the ODB++ output. IPC-2581 is a single .xml file that contains pads/traces/drill/net information.
Fortunately, you can export IPC-2581 from ODB++, and either of these two can be used to validate Gerber data as ipc-356 would. Most fabs have no issue working with ODB++.
Although I know that you and other customers in the same situation would prefer to have IPC356 as an option, it is not currently the format that Mentor is promoting for PADS Pro.
But as you found out through https://communities.mentor.com/ideas/16233 post that Mentor Engineering is considering it for a future release. So it will be available in the upcoming release. In the meantime, you can try the above suggestion to get around this.