According to the technical documentation, you should be able to use query flags on your parameters. See: https://docs.ifs.com/techdocs/23r1/050_reporting/256_br_and_a/005_adhoc_reporting/010_quickreports/#query_flags

However, the below doesn’t work for me at all. Perhaps the query dialog in IFS Enterprise Explorer modified the query on the fly, whereas Aurena doesn’t?

SELECT * FROM Shipment WHERE contract LIKE '&a-C--L]Site'

A cheat code I sometimes use is a function intended for operational reports: Report_SYS.Parse_Parameter. The first argument should be your data column and the second your query parameter. It accepts multiple values separated by semi-colon (;) wildcards (_ and as well as between (..), and returns TRUE or FALSE. You might take a performance hit though, so in your case I would use a sub-select to filter out the sites first like this:

SELECT * FROM Shipment WHERE contract IN (SELECT contract FROM Site WHERE Report_SYS.Parse_Parameter(contract, Upper('&Site')) = 'TRUE')