The source code for this tutorial is available on GitHub at: https://github.com/openmsa/Workflows/tree/master/Tutorials/Dyn_List_Workflow_Data_Provider
This tutorial explains how to use the variable type "Workflow Reference" to act as a dynamic data provider with a list of referenced workflow instances.
This is useful for calling a process from another process of the same workflow or another workflow as explained in Workflow REST API and Function Library.
The "data provider" workflow below has 3 instances
These instances can be listed with a variable "workflow reference" to allow another workflow to use these references and call a process from a selected instance
Edit the workflow variables and set the type to "workflow reference"
In the advanced parameters screen, select the workflow to refer to