At last I found a workaround, still would be cool to see a feature only for this, also is there a way to decrease the opacity of the layer you're not on?
Hello, thank you for the kind words! We plan on creating a tilemap editor eventually. As for your second question, right now it's not possible to decrease the opacity of non-selected layers. We should probably add a layer properties window that appears when you right click a layer that allows changing its opacity, in a future version.