If Bambu Studio had a option where you select a single object on a plate and you could select ‘clone max’ number of that object to fit on a plate based on it’s dimensions and print orientation. I could see 2 options. 1 to clone object the max amount with allowing the slicer to rotate the objects on the plate or 2, clone object max amount with logically lined up to fit on the plate.
I have found that the auto arrange is way to generous in leaving space between objects. It is a pain, but manually arranging will max out your build plate. My worst one was 18 small boxes. At least they were rectangles, so I just arrange 3 then multi selected and moved to where I wanted them.
My condolences. 
I make little cartoon letter magnets. Auto arrange was terrible, I had to manually move them too and keep adding more… 22 'Y’s, while screaming WHY?!(then carefully moving one by one)
I always say when I run into some stupid thing like this that there was blood on my desk from my beating my head on the edge …
and this not resolved yet? 
why can’t it be like cura? auto arrange works flawlessly bambu is awesome but this one little thing