The "Modify Variable" operation should work for order variables of list data type

Current Situation:

Users can modify the value of a variable when adding an order using the "Modify Variable" operation. However, if a list variable is present with other variables in the order variables, then the "Modify Variable" operation does not work.

Steps to reproduce:

• Create a workflow with a list variable and multiple variables with non-list type and deploy it.
• Each variable should contain an arbitrary value.
• Click "Add Order" in the Workflows view.
• Click "Modify Variable": nothing happens if we use the list variable.

Desired Behavior:

The "Modify Variable" operation should work with any combination of variables' data types.