Due to a fundamental change in how we perform authentication in Studio, we will not be able to restore this route as the flow that the endpoint uses will cease to work in the near future. The return-to-studio route was no longer used in any official Roblox products and traffic showed that this endpoint did not see any sort of regular use.
Could you confirm that the main UX improvements you are looking for are related to when you need to switch frequently between different accounts? We’re discussing internally how to improve the UX for these cases specifically.