Agreed, the terminology can be a bit much. Your screenshot sums it up! The "ArcGIS API for Python" is a mouthful in its own right!
Yes, myLayer refers the FeatureLayer. I should have been clearer.
gis = GIS(agol_url, agol_user, agol_pass)
myItem = gis.content.get(itemid)
myLayer = myItem.layers[0]
update_dict = {'metadata':'metadata.xml'}
myLayer.manager.update_definition(update_dict)
I don't see in the Feature Layer Manager a method for updating the metadata like you can for an Item using the update method. ( arcgis.gis module — arcgis 1.5.0 documentation )
It looks like I can update the properties that you see on the REST endpoint of the layer, but not the metadata associated with the layer.
Essentially, I want to automate the process of clicking the Metadata button (circled red in original post), clicking Overwrite on the metadata editor, selecting a local xml file and saving. It works for the Item metadata (blue circle).