Currently, it is possible to publish services on ArcGIS Server using query layers with parameters. However, these parameters are neither visible nor usable in Dashboards or Experience Builder widgets.
We could use this for managing this (really usual) situation : we have a feature class with polygon geometries (e.g., municipalities), and a table with time-related records associated with the geometries (e.g., one record per day and municipality for the last year in a 1:M relationthip) with values for a variable (e.g., births). It could be possible to create a parametrized query layer grouping the values of the variables (avg, max, min) for a specific time period (between ::date1 and ::date2 , e.g.).
Once the service is published, if it were possible to connect anyway those parameters (::date1 and ::date2) with the filters, e.g., It could be possible to apply symbology to the polygons using the (grouped) values of the variables. E.g. the user in the dashboard will select two dates and the map might show the polygons themed with the values resulting from the grouping of the variable. E.g. show the total/avg/max/min number of births -depending on how you built the query layer - in the municipalities between date1 and date2.
If I am not wrong, this type of query is not allowed for Dashboards or Experience builder, so it is not possible to apply symbology to a layer using the grouped values of a variable in a related table.
