Is there any way to add #tags to OSSN v4.2.
No:
But now its avilable https://www.softlab24.com/product/view/2355/hash-tags
Due to the many requests in the past for additonal features and components we have decided to develope a premium version. Features like Hashtags, Videos, Polls, Events, Stories, Link Preview, etc included in it.
$199 (Life Time)