I'm not sure what you mean...

You mean not at compile time?

If so, when registering models register different instances of the same model class, that has state to store how many inputs or outputs.

@russelltg

Not at compile time.
I need that when I put the block on the scene a window appears for inputting the number of inputs.
Now I solved the problem by passing the global variable to the class. When you register the model, the window does not appear. After registration, the value of the global variable is changed and when I put the block the window appears.

I also need this feature. Please add it. We are making an audio app and the user can put an audio block and configure later how many inputs/outputs it has.

I have done this for my own app. Eg: A node configures itself with the input and output ports of an incoming node. It has required some changes in the core code, namely that the number of ports and entries is assumed to be fixed when the node is first instanced... It would be nice if this came standard.