I have a Feature Service hosted on my ArcServer and exposed to the internet (something like this Layer: Rainfall(NOAA) (ID: 0)). I added this Feature Service to my AGOL org by going to Content > Create > Feature Layer > From URL and entering the REST URL of my Feature Service (I ended up with something like this: https://geodecisions.maps.arcgis.com/home/item.html?id=caa1b120e1ac4fa497866e0ba4cdcd9e). Now I would like to change the Feature Service to a different service on my ArcServer while keeping the same Feature Layer item id. Thie would allow me not to have to update the Feature Layer URL in a few applications that I have that use this Feature Layer. Is this possible? I have looked around in the Feature Layer settings and tried the ArcGIS Online Assistant but haven't found anything that works.
When you update the service URL pointing to the ArcGIS Server Feature Service on the Settings Tab of the ArcGIS Online Item, this change is not picked up in existing Maps and Apps. This is by design to prevent one layer modification from affecting potentially hundreds of maps.
However, you can update the URL from the Settings tab, then set the symbology, pop-ups, and labels on the Visualization tab, and re-add the Feature Layer to the Web Map. The Web Map at that point will pick up the changes, and the ArcGIS Online item ID remains unchanged.
Hope this helps,