If you make the query in the UI, and the save it. You can create a second query on saved workbooks and can get the xml version of the query (or there might be a more sane way to do it). You should be able to get the needed

target

from the xml object it provides for you if

memberitem

is not correct.

Additionally, the component joins are not necessary in code at all. You can add the string representation of them to your result or criteria columns and that will work fine.

var queryMain = query.create({
    type: query.Type.TRANSACTION
});
queryMain.condition = queryMain.and(
    queryMain.createCondition({
        fieldId: 'type',
        operator: query.Operator.ANY_OF,
        values: ['TrnfrOrd']
    }),,
    queryMain.createCondition({
        fieldId: 'transactionlines.item^item.locations.location',
        operator: query.Operator.ANY_OF,
        values: fromLocation
    })
)

queryMain.columns = [
    queryMain.createColumn({
        fieldId: 'transactionlines.item'
    }),
    queryMain.createColumn({
        fieldId: 'transactionlines.units'
    }),
    queryMain.createColumn({
        fieldId: 'transactionlines.units',
        context: query.FieldContext.DISPLAY
    }),
    queryMain.createColumn({
        fieldId: 'transactionlines.rate'
    })
]

Somehting like this for example will run perfectly fine