Parameter rules over two or more lines do not work in workflow mode

This works:

tab = ((numbers: 1, 3), (strings: 'a', 'b'))

but this does not:

tab = ((numbers: 1, 3),
       (strings: 'a', 'b'))

Syntax error: None:2:8 --> ),        *(strings:  <--
Expected '\s*(^|;)' or EOF

The issue is caused by the surrogate grammar used to parse the vary statements.