Building Block A depends on Building Block B. Building Block B produces an output that is a list of parameter values (e.g. available sizes, names, or IDs). Today, Building Block A's input cannot be populated with this list; the user has to manually type in one of the valid values, which is error-prone and creates a poor user experience for the Platform Team's end users.

Allow a Building Block input to be configured as a dropdown (single-select) whose options are dynamically sourced from a list-type output of a dependent Building Block. When Building Block A is run, the dropdown should automatically show the current values from Building Block B's output instead of requiring free-text entry.