In WoW Classic, you can only track up to 5 quests at a time, and quests will fade from the tracker if you aren’t actively working on them. To enable this option open the Main Menu (ESC), click on Display, and check Automatic Quest Tracking.
In WoW Classic, a quest will automatically appear in the tracker only when you complete an objective towards the quest, and you have Automatic Quest Tracking enabled. In World of Warcraft, a quest will automatically be added to the tracker as soon as you pick it up, or each time you complete an objective towards the quest. In the default World of Warcraft interface, the quest tracker appears under the mini map.
