WebIQ supports OPC-UA methods since V2.10. However, a script is required to call the method.
In the attached example, I have implemented a UI action to call the "sqrt(x)" method on our OPC UA online demo server.
To enter the method (see Process Data Manager) you can browse the OPC-UA namespace and import it by right-clicking on the method. An OPC variable with the name "sqrt(x)" appears and at the same time a method in the "Methods" tab.
I wish you success
Here you find the information what you have to do in ctrlX Engineering to make a PLC method callable via OpcUA.