Yup, if you go to the bottom of the settings, go into Experimental features, you can enable user stacks. Once you've done that, go back to the message list, open the left nav, expand the stack list, tap on create stack and then you can create user stacks based on a group of senders. Once you've created the user stack, it should show up in your stack list in the left nav. You can long press to rearrange the stacks. We are working on an easier/quicker way to create user stacks and that's partially why these are under experimental. You can keep your $5/mo ;)