The "crafting combinator" shows, in the right-side info pane, its input signals but it doesn't show the output signals. I have to connect it to a power pole to see that.

That's because the entity you interact with is not actually the entity that produces the outputs - there's a hidden constant combinator connected with invisible wires to the output side to do that. It's done this way because none of the two-tile combinators can have their outputs set to arbitrary signals by script (at least that was the case when I implemented this). Also, as far as I know, there's no way to set what's going to be displayed in the info pane directly either...