Only show group summary in Gannt Chart

Is it possible to only show the group summary in the Gannt chart?

I want to have a fairly detailed timeline of each project (using the Timeline view) and a Gannt showing a single line per project (using the Gannt chart and ideally the summary line of each group - this automatically calculates the start and end date). This will give me a high level summary of the portfolio (for exec level people) and a more detailed version of the plans for exec-1, but all coming off the same board and data.

I would like to have multiple projects in a board, one group per project.

I would then like to use the timeline view to show a sequence of critical tasks from each group (I can use a checkbox to mark these and then filter on that to give me this view).

I would also like to have a Gannt chart, based on the same board, to give me a single line per project. The summary line would be perfect as it’s got the group name and duration. I don’t see the group line unless I have at least one other item showing in the Gannt (I can filter all items out but then the summary doesn’t show).