Sadly there is very little publicly documented about Amadeus. The manuals are very “hardcore” reference material and hard to understand. I have them somewhere as PDFs and can try to locate the specific topic.
That said, the ba-command is very easy to understand.
ba0 = full beam
basomething beams in “something” where something is the “duration value” or a list of “duration values”.
ba4,4,2 would beam quarter-quarter-half
ba4,2,4 would beam quarter-half-quarter
ba4.,16,2. would beam dotted fourth, 16th, dotted 2.
The “something” is then cyclic, meaning it would repeat itself until the next ba-command.
in 4/4 would not be needed since ba2 would suffice.
In the same way in 3/4
is not needed as ba4 suffice.
As with time signatures in Dorico Amadeus can assign individual ba-commands to each stave, making it easy to beam differently against each other if that is wanted, just as you can have different time signatures in Dorico.
I could see this as a very useful function (with signpost) in Dorico.
The “plain” ba command in Amadeus cuts any beam (once) but I think Dorico’s “Split beam” is as good (if not better) as it would mean a lot of signposts (but they could be hidden naturally).
Further, a “sister command” in Amadeus to ba is “vocal” that cuts any beam to individual flags, e.g. for old-styled choral music.