I've been using this for a few days now and it's so frustrating because if it was only just a little more flexible it would be fabulous but as it's so rigid it's just infuriating. The top three slots on the list are OneDrive root, ODB root and Documents; none of those are where I ever save any documents. The other slots are populated by 4-5 of the 10-12 folders I use frequently. If the folder I want is on that list, It's perfect. But I can't pick what I want to see there or remove the top 3 I never use and replace them with 3 useful folders, so it's one extra click to get to where I can navigate almost every time. That means I never voluntarily use this dialog because I can't remember if the folder I want will be on the short auto-populated list or not, so I just avoid it entirely.
to make this useful rather than annoying; let me choose how many slots to have on the list. If I want 12, give me 12.
let me choose what's in every slot; don't put a folder I will never use in the way and make me click and scroll past it every time.
I bet admins would like a GPO to autopopulate those folder slots and pin folders based on things like group membership.
this is about half way useful; make it flexible and it will be great instead of infuriating.