IBM® SPSS® Amos™ 28

You have all the capability of a general-purpose language (Visual Basic or C#) available, so that you can estimate any computable function of the model parameters.

The CValue class is used to specify general user-defined estimands.

This link supplies several examples of general user-defined estimands including videos.

Sometimes this general approach to user-defined estimands is overkill. A simplified method for specifying user-defined estimands is also available. The simplified method has some limitations, but is  easier to use.