To add a reason box below and connected to a desired box, select the desired box and either use the Add reason button in the control panel at the top of Argumentation.io (the button with the green plus sign inside the circle) or press Shift+Alt+R. Here are instructions on selecting a desired box.
When you add a reason, it automatically comes with two objects between it and the box you had selected when you added it. These two objects are the inference node and the reason group box. For example, if you had the main contention selected when you added a reason, an inference node will be added below the main contention, and a reason group box below that, and then the reason you added will be inside this box.
When you add a reason, it will be automatically selected.
Objections work the same way. The Add objection button is also in the control panel at the top of the Argumentation workspace (the button’s icon is a red line inside a red circle). The key command to add an objection is Shift+Alt+O.
To add co-premises in Argumentation:
Select the desired reason or objection box.
Click the Add co-premise button in the control panel (the one with the black plus sign inside the black circle) at the top of Argumentation or use the key command Alt+Shift+C. This adds another reason (or objection) inside the reason (or objection) group box of the selected reason or objection. It will appear, to the right of the one you selected when you used the add co-premise function.
This co-premises looks and behaves just like any other reason or objection. You can write in it, select it to add reasons or objections to, add co-premises to it, and move it around.