import omni.kit.widget.layers
# set current focused layer
omni.kit.widget.layers.set_current_focused_layer_item(some_layer_path)
def on_layer_selection_changed(item):
layer_item = omni.kit.widget.layers.get_current_focused_layer_item()
if layer_item:
# do something on layer selection changed
pass
# subscribe layer item select change in layer widget
omni.kit.widget.layers.add_layer_selection_changed_fn(on_layer_selection_changed)
# remove the subscribe function
omni.kit.widget.layers.remove_layer_selection_changed_fn(on_layer_selection_changed)