See https://github.com/geoadmin/mf-geoadmin3/commit/a407fa72f06f18de89d8f8be5bdffc49ee0812b8 for an attempt to remove item.preview and rely on layer.preview only. But this actually changes the behavior. This:

1. Move over the swissALTI3D layer, the layer text changes to grey. SAME.
2. Click to add the layer to the map, the layer text changes to red, while it stayed grey previously. DIFFERENT.
3. Move out of the layer node, the layer text stays red, while it changed to red previously. DIFFERENT.
4. Move over the layer again, the layer text stays red, while it changes to grey previously. DIFFERENT.

I think that the new behavior is better, because the color always correspond to the actual state of the layer. Previously, the item could be selected while the layer was not, and vice-versa.

I need feedback from "usability" people I guess.