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To change the UV tiling in the material, you
- create a ‘TextureCoordinate’ node and plug it into the ‘UVs’ pin of the ‘TextureSample’ node
- click on the ‘TextureCoordinate’ node and change the ‘UTiling’ and ‘VTiling’ properties
See also Coordinates Expressions | Unreal Engine Documentation
To change the UV scale in the BSP surface, you
- select a surface with Ctrl + Shift + Left Click on it
- change the properties under ‘Details’ -> ‘Surface Properties’ -> ‘Scale’
See also Geometry Brush Actors | Unreal Engine Documentation