Yes - all product vendors who choose to undertake the challenge of data visualization, paint themselves into a corner that precludes a win. If instead, they would focus on the integration adhesives that make it easier to lean on D3, Vega, Charts.js – they would be able to put a checkmark in the win column in 80% of the cases while giving customers the ability to help themselves in the remaining cesspool of deeply complicated data visualizations that arise.
Rose. There is a workaround to do what you would like. In short, you have to use a formula to create a "grouping category" and group your gant chart by that.
This may sound a bit esoteric, so I attached a picture of what I'm doing:
I'm a product manager, so prioritization of Initiatives is key for me.
And having their associated Epics, in priority order, then features and tasks the same, is key as well.
Problem is, as you found, AirTable only does things by earliest to latest.
In my case, I created a formula field and concatenated the name of the work with a number from a sequential number field.
This forces a "stack rank" order of all items that will be respected when you group by that concatenated "grouping field"
This video goes over it really well (I'm not associated with the dude who made it, lol) : https://www.youtube.com/watch?v=2mMbyRY-6E0
I really banged my head against the wall on this one.
You can also add a custom extension that will automatically renumber/stack rank your table and that can be used for your "grouping field". It's called "Save view ordering to field".
I hope this helps!