"Maximum Number of Records Returned by Server" ("maxRecordCount") cannot be modified from ArcGIS Server Manager for hosted maps and Feature Services.

Workaround

1. Modify this property when publishing the Hosted Map or Feature Service from ArcGIS Pro.
   1. Ensure that you have made an active portal connection in ArcGIS Pro to a Portal for ArcGIS that has a designated hosting server with an associated ArcGIS Data Store.
   2. Add a dataset as a layer to a new map in ArcGIS Pro, and choose to share this layer as a Web Layer.
   3. In the Share As Web Layer pane, choose Copy all Data.
   4. Under the Configuration tab within the Share As Web Layer pane, click on the Configure Parameters button.
   5. Under Properties, there is a "Maximum records returned by server" parameter that can be modified.
2. Modify this property after the service has been published within the ArcGIS Server Administrator Directory.
   1. Publish a hosted map or feature service to Portal for ArcGIS from ArcGIS Pro. 
   2. Navigate to, "https://[fully qualified domain name]/[name of web adaptor configured with ArcGIS Server]/admin".
   3. Navigate to, "services", and click on the Hosted Map or Feature Service that was previously published.
   4. Scroll all the way down the page to find the "Supported Operations" option for this service, and click on Edit.
   5. You will then see a JSON object containing various properties associated with this service. Within these properties, you will find a property called "maxRecordCount". Modifying this property will allow for you to change the maximum number of records that can be returned by the server for this particular service. 

Steps to Reproduce