FleetingClouds Whoops, sorry for the late reply! I thought I had answered this, but I guess it didn't send through.
There is no way of telling the difference between a novel undergoing a hiatus and a novel that's currently being written. There are no tags or special flairs that tell you, unfortunately. It's been asked for a few times in the translations side of things.
Generally, unless the author has said they're going to drop the novel or say/ do something that says that message, the novel's been dropped. If a novel has a low number of chapters and hasn't had any recent updates, assume the same.
If the novel has a constant release rate/ recently added chapter you can assume that it's currently being written. If a novel has a high number of chapters but hasn't had any recently written chapters, something must've happened to the author.