Hi!
Unfortunately, you can’t do the same trick inside Unreal. But you can make a similar one.
Here is my setup :
I have a custom mesh with two different UV Channels
UV 0
UV 1
Here, I offset my UVs by a parameter and ceil it to fill the UV Tile with a value of 1. Then, if it’s not equal to 1, it will return 0; if it’s equal, it will return 1. This will create the mask to lerp between your textures A and B. (As if you add more offset, the ceil will return 2, then 3, etc.)
I think there is a simpler way to achieve this mask, though. However, this is the first idea that came to mind