I personally have never heard "go malling" although that may be because we don't call a large building full of shops a 'mall' like they do in the USA. We tend to prefer 'shopping centre'. 'To go shopping' is fine in either circumstance, but if you go with the intention of just browsing like Bachstelze suggested, you can say "to go window shopping"; i.e. you only look in the windows!

"Go malling" is going mall-hopping. A person would go to the mall to hang out, like Bachstelze has already said. BUT, it doesn't have to be just ONE mall, rather, it can be several different malls. This is especially true if you live in an area where there are several malls close to one another. Hope this clears everything up! :)

I've also never heard "go malling", and that's with extensive exposure to both US English and British English. Lewis's answer is spot-on.

To go malling is to go to a shopping mall without intending to buy anything, just to pass time.

I couldn't find the word 'malling' in any dictionary. But, I heard some people using it. Is go malling a newly coined-word that means go window-shopping by people in their teens ?