Auto populate field- Next Sequence

[TeaganJahn]

Is there a way to auto populate a field for new features in a hosted feature layer?

I'm currently manually inputting in the next sequence for the FIELD_REF. I understand attribute rules isn't supported for feature layers. 

[Laura]

Having a letter in front of your number is going to complicate things.

An idea I would upvote: https://community.esri.com/t5/arcgis-online-ideas/support-for-attribute-rules-in-arcgis-online/idi-p...

I had a similar issue with unique IDs being calculate in ArcMap before me with P in front of the numbers. I reached out to Esri support for a solution (layer is now just on AGOL) and this is the documentation they provided me:

• Add unique constraint to ArcGIS Online Field 
• Create and Manage Attribute Rules - ArcGIS Pro
• How To: Add auto sequential values using attribute rules in ArcGIS Pro
• ArcGIS Community: Attribute Rules for handling a unique internal ID

I was also able to add ENH-000126768 to my case in hopes of pushing things along further.

In my case only a few rows are added a year (when something is split) so I manually update that field.