Tags are words or phrases that you can assign to tasks. You can then view all tasks with specific tags together to have a better view of your actions and their effects.
Tagging tasks allows you to group them together under a common goal (such as "persistence on bob's box", "getting objective 1", etc). You can then easily go back and view not only all of the tasks together, but all of the resulting metadata that Mythic knows about surrounding those tasks.
Use the dropdown for a task's status to add/remove tags.
From the "Operational Views" -> "Tasks by Tag", you can select your desired tag from the top right of the screen. Not only are you able to view all the tasks, status, and outputs, but you can also see all of the aggregated information for all of the tasks with that associated tag such as:
All of the files (uploads and downloads) that were generated as part of all of the tasks
All of the artifacts generated as part of all of the tasks
All of the MITRE ATT&CK techniques associated with that group of tasks
All of the credentials associated with those tasks