You have to modify .gmfgen model in this case. Try openning this file, locating
GenCompartment instance representing compartment inside a pool and setting
"isListLayout" property to true for this compartment. Note: due to the current
GMF limitation this property will always be re-set to "false" on upcomming
.gmfmap->.gmfgen model transformations, so you should take care on setting
this property to true in the end of each transformation.