Passing multivalued Parameters into Report Viewer in Web Designer

I have created a custom IT Shop component - used the wizard to add a link to a custom report.  Works fine without providing values for the parameters when compiling the report - using the default values provided in the report definition.

 One of the report parameters is defined as multivalued in the report definition - however I cannot find a way to pass multiple values into the "Compile Report" node in Web Designer.

Tried comma separated list, char(7) separated list , basic "from xxx select yyy" result set  . . . no luck . . .

Anyone know how to get multivalues from IT Shop into Report Compiler ?