I’m not sure what you mean by tree function. To summarize what I’ve been telling you:
There is an existing tree in tree.js that appears on the left side. If you want to add new nodes to that tree, you typically will want to create new layers (in layers.js to keep it simple) and they will be AUTOMATICALLY added to that tree based on their row and position properties (see [this docs page](The-Modding-Tree/layer-features.md at master · Acamaeda/The-Modding-Tree · GitHub for those and the other tree/node related properties). You can technically manually set the nodes for the tree, but if all you are trying to do is add a new layer and have it appear on the tree, you won’t need to change a single thing about the tree code - just create the new layer (you can literally copy the code you have for the first layer, then modify from there) and make sure it has the row and position you want.
If you want to create a NEW tree, you’ll need to make a custom layer display using tabFormat. See this docs page on how to do that. The specific code for this NEW TREE will look like ["tree", ARRAY_OF_ARRAY_OF_LAYERS]. But again, that is only for a NEW TREE.