Okay, I've made some progress with this but I've run into a problem. My node appears in the 'Uncategorized' section in the asset browser, as expected. The layout in the resource editor looks like this:
The preview in the resource editor is this:
Which is all good. But when I add it to the node editor, what appears is this:
Instead of the strings I expected ('Input A' etc.) I just get what look like default strings. However, in the attribute manager I can see my attributes and these default ones:
The node does work, all it does is add two integers, and if I put values into the two input ports the results appears in the output port. But why don't I get my input and output ports instead of these apparently default ones?