Hello,
Sorry that you couldn't find this information! It's a gap on our side, and we'll add guidance in our upcoming refresh of the docs at madeira.microsoft.com/.../finance-dimensions
As Chris mentions, the Dimension Combinations matrix is for restricting specific combinations of dimensions. Is this what you are trying to acchieve? If not, my recommendation would be to set up two dimensions: Division and Department. The Division dimension would have two dimension values, and the Department dimension would have 3 dimension values.
In either case, my team will provide better examples of how to use dimensions in the upcoming update.
