Answer:
If no angle can be defined in the "Rotation" column, an isotropic material model is selected for the material where stiffnesses are identical in all directions and it is not necessary to define an angle.
If you use materials with anisotropic behavior (for example, timber), it is necessary to ensure that the "Orthotropic | Linear Elastic (Surfaces)" material model is selected.
Note: The "Orthotropic | Timber | Linear Elastic (Surfaces)" material model cannot be currently used in combination with the "Layers" thickness type.
After switching to the orthotropic material model, the individual layers can be rotated accordingly.
