I just tested this with Visual COBOL for Visual Studio and although it accepts the Pro*COBOL option of format=variable when I try to change the project directives to use sourceformat"variable" I receive the following:
CSQL-F-047: Cobsql cannot be used with the SOURCEFORMAT directive
This tells me that this is not currently supported as you suspected.
I will check with development to see wat the plans are for supporting this.
Thanks.