Can't add a range to composite query where JoinMode is ExistsJoin

I have an AOT query that has the SalesTable as a datasource and joins to CustTable (JoinMode: ExistsJoin). I can add ranges on both the SalesTable and CustTable datasources.

When I create a composite query using this query I can add an additional range to the SalesTable datasource but not the CustTable datasource.

It seems only to be the case with ExistsJoin and NoExistsJoin as InnerJoin works as expected. Is this a limitation of composite queries in AX and can anyone suggest a solution that has maybe encountered this before? My next step was to look at how I can set this range in code.

Thanks,

Toby