Grouping
Every grouping can be (currently) done by parenthesis. So the parenthesis may be both “real” parenthesis and grouping ones.
For example, these parentheses specify nominator of the fraction:
$ (a^2 + b^2)/2 $
Left-right
If there are two matching braces of any kind, they will be wrapped as lr (left-right) group.
$
{[((a + b)/2) + 1]_0}
$
You can disable it by escaping.
You can also match braces of any kind by using lr directly:
$
lr([a/2, b)) \
lr([a/2, b), size: #150%)
$
Fences
Fences are not matched automatically because of large amount of false-positives.
You can use abs or norm to match them:
$
abs(a + b), norm(a + b), floor(a + b), ceil(a + b), round(a + b)
$