Await app.activeDocument.activeLayers.merge()

[Karmalakas]

activeLayers never had a merge method. Layer has one. Not a solution, but this might give you some insight:

Multiple active layers + Layer.merge() = Confusion

I’m looking for the right way to merge multiple layers at once. The description for Layer.merge() in the documentation says the following (see here): Merges layers. This operates on the currently selected layers. If multiple layers are selected, they will be merged together. If one layer is selected, it is merged down with the layer beneath. In this case, the layer below must be a pixel layer. The merged layer will now be the active layer. So it sounds like Layer.merge() should do two differ…