This is an addon for Godot 4.2+ that adds a Detail node to the visual shader editor. This is used to blend a secondary normal and albedo map.
This feature exists in StandardMaterial3D. The blend modes available are Mix, Add, Subtract & Multiply. These are fine for albedo, but doesn't work well with normal maps. So the blend modes in the node affects only the albedo. The normal maps are combined using the UDN method.
The Mask input controls where the secondary textures are applied & Normal Strength controls the detail normal strength.
Note that both the albedo & normal map inputs need to be connected for the outputs to calculate.
Extract the zip file and copy the folder to your project. You'll need to restart the editor for the node to appear in visual shader. Alternatively, you can make a new gdscript file and copy the code.