Filter in columns

Since build 8.0.1545 it's now possible to specify custom row data (tags) and use them in onRowFilter:

dp.resources = [
   { name: "Room A", id: "A"},
   // ...
   { name: "Room J", id: "J" },
   { name: "Room K", id: "K", tags: {alwaysVisible: true} }
  ];

Using tags during filtering

dp.onRowFilter = function(args) {
  if (args.row.name.toUpperCase().indexOf(args.filter.toUpperCase()) === -1) {
    args.visible = false || (args.row.tags && args.row.tags.alwaysVisible);
  }
};

See also:
http://doc.daypilot.org/scheduler/row-filtering/

I am using the javascript trial version. Where can I download build 8.0.1545?

You can download it in the sandbox:

http://javascript.daypilot.org/sandbox/