This parameter allows the simple list attributes (the attributes that specified in the GML2 DEF lines with a “{}” suffix) to be carried in the FME features as multi-value attributes.
When set to Yes, the GML2 writer will not expect the FME features to contain simple list attributes; instead, every attribute that is defined in the DEF lines with a {} suffix is expected to be a single attribute such that its value is a token separated lists of values, a multi-value attribute.
Can be used in conjunction with: Multi-Value Separator