A lot has changed since 2010 when I built my first Shopify store, but most of those changes have been geared towards Shopify customers/brands as opposed to Shopify Partners. For that reason I'm super excited noticing some of the recent updates on the Partner side of things like this one. Hopefully these advancements keep coming!
Anyway, in the past it has always an awkward when the project comes to a conclusion with a client. Final payment has been made, store ownership has been transferred...but wait! What kind of partner would we be if we didn't finish linking up the clients custom domain now that they're on a paid plan (new stores) or look into any final questions they have before going live? Hence the awkwardness of having to ask for a Staff account or in more recent history a Collaborator account.
Luckily there's this nifty new option to transfer development store ownership from the Partner Dashboard - at the same time remove any existing credit cards used for billing. This also automatically creates a collaborator account!
I didn't see any announcements screaming about this anywhere else, so hopefully this is helpful to all you Shopify Partners out there! =P