$_POST.<variable> is this possible?

Wappler 6.8.0 Node project.
I want to access data coming from post-call in a loop for a few fields. eg
$_POST - { "A":1, "B":2, "C":3}.
X=[A,C]
Loop over X as x
#_POST.x

Obviously you mean that you have a $_POST variable type of Object...
And you want in your API to pick any nodes from within this object (for example only A & C) and loop through those?

Please explain a little more...
Give us an actual example so we have something to go on

You can dynamically access variables like:

$_POST[variable_name]
$_POST['A']

You can also use a Repeat step with expression $_POST and it'll iterate through all fields