Submixes are so convenient. They make global audio adjustments to specific tracks easy by grouping them into one mix. In this Premiumbeat tutorial, Jason Boone shows you how simple it is to create a submix track in Premiere Pro. Submixes are also a great way to create audio stems of your dialogue, music, SFX, etc.
Need to apply audio and effect changes to multiple audio tracks — all at the same time? No problem. Follow these steps to create a submix in Adobe Premiere Pro. —Jason Boone, Premiumbeat Blog
Source: https://www.premiumbeat.com/blog/create-submix-in-adobe-premiere-pro/