In cases where you may not want to type the full name of an attribute that is at the same level as the attribute being expressed, you can enter expressions that refer to an input by its short name.

For example, if you want to add an expression to the Gaussian Rotation based on the value of the Gaussian X Radius, instead of writing out the long expression, you only need to refer to its short expression.

This applies to all grouping levels, be it inputs on a node, or inputs in a structure, or inputs on a node that is in a group.