The grain-texture is an image-file.
Let’s say you have a ‘…vertical’ texture material.
Save its image-file externally and edit that with an app like Gimp and Rotate it so it’s vertical.
Now in SketchUp make a new material based on the vertical one.
Name it ‘…horizontal’.
Swap its height and width values, and link its texture to the image-file you have just edited.
Now you have two materials - a horizontal and a vertical version.
Save those materials to a Collection, located on one of your normal Materials paths…
Now in other projects you can access either version as desired.
Repeat with other grained materials as you wish…