There are 3 types of sliders.
These sliders are available with every Sequence account and can't be edited or deleted.
You are in full control in which workouts should have these widgets.
When a sliders is added to a workout you will now see a new section when completing a workout.
The reason for adding sliders to workouts is it gives you a great insight into the overall "big picture" of your training.
Each time you complete a workout that has a slider/s the data is captured and represented within the metrics snapshot section like so.