Hi guys, im using this image as an example - https://dribbble.com/shots/4156433-Mail-client-app/attachments/950266

Hi guys, im using this image as an example - https://dribbble.com/shots/4156433-Mail-client-app/attachments/950266

I Want to modify the treeview style so when I select an item it will that blue vertical rectangle next to it where it says inbox.

Does anybody know how to do this ?
https://dribbble.com/shots/4156433-Mail-client-app/attachments/950266