Our goal has always been to build simple support tools. In Groove Inbox 2.0, when we looked at how to simplify things, one of the features that didn't make the cut was 'pending' status.
Instead of marking tickets as "pending" we recommend utilizing our Snooze feature -- the little clock icon you see at the top of the conversation page.
Snoozing conversations works in a similar way, but has the additional functionality of re-opening the conversation at the end of the snooze period. One common trend we saw with customers is that "pending" tickets would often be forgotten about, but with Snooze the “unsnoozing” action works as a reminder so that conversations no longer get lost if the customer doesn’t follow up.
If you prefer not to snooze your tickets, alternatively you can use tags to mark your conversations as “pending” and then easily see all of your “pending” tickets together in a list.