You would need to override string filter, something like (untested):
Ext.define('MyOverride', {
override: 'Ext.ux.grid.filter.StringFilter',
validateRecord : function (record) {
var val = record.get(this.dataIndex);
if(typeof val != 'string') {
return (this.getValue().length === 0);
}
val = val.toLowerCase();
var parts = this.getValue().toLowerCase().split('|'),
found = false;
Ext.Array.forEach(parts, function(part) {
if (val.indexOf(part) > -1) {
found = true;
}
});
return found;
}
});