TX ultimate can not be used in place of existing multi-way switches directly, but there are two ways to achieve that:
1. with 2 TX ultimate switches
One switch(A) connects to the light, the other switch(B) does not
and then set the following scenes on each of the two switches to synchronize the two channel states to achieve a similar effect of dual control
If A on then B on
If A off then B off
If B on then A on
If B off then A off

2. With one TX Ultimate and one R5 Scene Controller
R5 can control the device which has the eWeLink-Remote gateway feature even offline, 90M remote control without Network while TX Ultimate is a smart switch with the gateway function of “eWeLink-Remote“, so you can connect tx ultimate to the light and then add R5 to the tx ultimate, set smart scene, then you can use R5 and TX ultimate to control the same light