I assume you are talking about chord nomenclature here and not popover syntax, but the brackets would add a lot of unnecessary clutter. Root - Quality - Extension - Alteration is the standard formatting that everyone understands. If you use sharps and flats for alterations, then you need to use parentheses so there is no confusion with the root accidental, i.e. Ab6 or A(b6). If you use + and -, then there is no need for parentheses. (Minus really should never be used for the quality of minor in the computer era as it was just a hand copying shortcut.)
Why would you possibly use Dm(m7) when Dm7 is perfectly clear? The 7 always means a minor 7th unless prefaced with maj, ma, +, #, etc, in which case it is major, or diminished 7th if used with dim or the dim circle.