GanttProject with similar MSProject timeline feature. Example attached

Hello all,
I have been trying to get an example of how could I emulate the feature called “timeline” in MSProject 2013+.

The idea is to get some tasks “on top” that are linked to the schedule, and are automatically updated. In MSProject you can set a value to be a reference to another cell (as Excel does); but not sure in GanttProject (i.e. make two tasks to share the same duration value in a single cell).

So, I tried it with dependencies.
See example attached.

How do GanttProject users get “timeline” views and summaries from their detailed schedules?

Thanks all! Regards, M.