Adding new layer to hosted feature layer

Question

Maybe this is a completely stupid question, but I haven't found a solution anywhere. Is there any way to add a feature layer to an existing hosted feature layer? I have a hosted feature layer that contains multiple layers and I want to add more layers, how can I achieve this?

Katie_Clark · Answer

Unfortunately, as @MobiusSnake mentioned, there really isn't a good way to do this at the moment. I created an Idea for this a while ago, so feel free to give it a kudos and comment if you want to get it supported.

https://community.esri.com/t5/arcgis-online-ideas/add-and-remove-layers-to-existing-hosted-feature/idi-p/1028128

MobiusSnake · Answer

As far as I know the only way to do this is via the administrative REST API.  There's an "Add to Definition" call you can use to throw new layers and tables into your service as JSON.  You can follow that up with an "Update Definition" call to create relationships between your new datasets and your old ones as well.

I would 100% not recommend doing this out of the gate on any production services you've got though, it's super easy to botch it.  To be honest I generally avoid doing this unless all other options are significantly more work because it's so easy to mess up and hard to fix, it's a risky play.  And absolutely back up your service's data before you try it.