The Node Lists are designed to work only on the first, base planet since is is the most common use. To change surface and atmosphere settings and add new shaders to additional planets, you need to access their internal node networks, which you can do in several ways:
From the additional planet node's settings, press the gear icon button upper-right, then select "edit internal network".
In the node network double-click the + on the right side of the additional planet node, or right-click the node and choose "Internal network".
Once in the internal network you add additional shader and atmosphere nodes with the node network controls. You can right-click to get a menu of options, or press Tab and type the name of a node to search, for example. You can emulate how the main planet is setup in terms of shading and atmosphere node configuration if you need guidance.
You can also use the green "+" button next to the "Surface shader" and "Atmosphere shader" fields in the settings of the Planet node, and choose "Go to [node name]" to access the settings of the node directly connected to the planet internally, however this is quite limited as it doesn't let you see and access any additional nodes connected to them, so I recommend exploring the internal node network as above, and adding nodes directly there.
- Oshyan