Edit All Layers button
This only works with a special layer created in Affinity Designer Layers.afdesign
This allows you to work with many objects in a particular layer, ignoring everything except this layer.
This way you can work with a very complex design without being afraid of accidentally moving objects on the bottom layers.
You can also change the layer label color, by right-clicking on the layer > Properties. This will also change the bounding box color.