How to merge Thread from HomeAssistant and HomeKit networks?

I have also 2 Networks.

Years ago I merged my Home Assistant Thread Network with AppleTV-Thread. Now there is the new Ikea Thread-Network after the Dirigera-Hub got its firmware update last year.
But I found no way to merge these 2 networks.
The Ikea app doesn’t even show that there is a Thread network, let alone an option to switch networks.

Did anybody know how to add IKEA’s OpenThread network to the HomeAssistant one?