DT1 widget: subtitle type scrollbar should be a drop-down

<img width="375" alt="Screen Shot 2021-06-06 at 7 48 37 PM" src="https://user-images.githubusercontent.com/936440/120952582-37801380-c700-11eb-9e23-950158994634.png">
This scrollbar would make a lot more sense as a drop-down.