I decoded .litematica file as nbt, and got json. In the BuildingPlacementName i have "BlockStates", "Position" ... "BlockStatePalette" ... "TIleEntities".
How to decode "BlockStates"?

Part of "BlockStates"

...
[-2147483648,39321606],
[31738240,1131675659],
[0,236716032],
[49670500,1074724864],
[575344131,-1607475524],
[14448,15],
[-1517211076,0],
[698705,-1894364040],
[-507510784,3989872],
[2013265920,0],
[21132521,-744009628],
...

It's a bit-packed array of IDs that refer to the palette indices. It was previously discussed a bit here: #53

Oh, I'm sorry.
I seem to be blind