Sorry, but I haven't tried it and have no use for it. However, I did ask the AI Perplexity (one of the best and most neutral, in my opinion) and here's its answer:
Yes, it is possible to have 2 remote controls that work with the same Steffen sockets, because the frequency used is identical (433.92 MHz).
You simply need to pair each remote with the sockets you want.
In this way, several remotes can control the same set of sockets or different sets, depending on the programming.