There are 3 usages of the $ character in a DOSKEY macro.
$T is the equivalent of & in a batch script. One can join commands together like so.
DOSKEY test=echo hello $T echo world
Like bash(not batch), we use $ to indicate command-line argument.
$1 refers to the first command-line argument
$2 refers to second command-line argument, etc..
$* refers to all command-line argument