...
var mySalesOrderSearch = search.create({
    type: search.Type.SALES_ORDER,
    title: 'My SalesOrder Search',
    id: 'customsearch_my_so_search',
    columns: [{
        name: 'entity'
    }, {
        name: 'subsidiary'
    }, {
        name: 'name'
    }, {
        name: 'currency'
    }],
    filters: [{
        name: 'mainline',
        operator: 'is',
        values: ['T']
    }, {
        name: 'subsidiary.name',
        operator: 'contains',
        values: ['CAD']
    }]
...