Multipoint pairing is indeed very desirable to give the UTWS lineup a completed features package (plus some improvement on the software side).That's a good workaround idea, @Ocelitgol especially if their use case isn't latency sensitive.
@Nokduangrach FWIW the QCC3020 used in the UTWS3 definitely does not support what is commonly referred to as multipoint pairing. I will also stress that basically no TWS adapters have chipsets with multipoint ATM. Some of the larger BT adapters, e.g. my ES100 do. As a compromise, although not exactly helpful for your use case, I'm urging @FiiO Willson to suggest that the engineering team revise the connection handshake behavior to accept/change to the new device on a new connection request instead of rejecting any new requests if a device is already connected. This will at least make it faster and easier to switch between devices in lieu of multipoint. This is common (Pixel Buds, Sony wf1000, etc. all work this way).
I also remember that Samsung has some kind of seamless switch between different Samsung devices (there is an option for that on the Galaxy Buds Plus app). But to be fair, Samsung did use their own chip for that (correct me if I am wrong).