How can I view the list of collectibles and side activites in the current location?
When hovering over fast travel regions, the game displays for each available collectible type and side activity how many are already completed and how many are available: 
However I cannot seem to find a way to see this overview for the current location I am im. How can I view this information for the current location?
From Primagames:
You can hold the Right Bumper on Xbox Consoles, use R2 on PS3, R1 on PS4, and the R button on the WII U.
Not depicted on the website, but you can use your mouse's Scroll Wheel to view Collectibles on PC copies of the game.