In argument visualization, you can add an objection to a whole argument, not just against a specific proposition. That's great and important, since you may want to accept the truth of all premisses yet deny that they support the conclusion.

But right now, visually, it's a red line appearing inside the green brace. It's not clear. Maybe anchoring a red line in the green line of the argument against which you level an objection would be clearer.