How sort by date/time on Kibana Discover

Probably you can, I never tried until now.

es01

You can add fields from the list left to the result list, then you can sort by them. Maybe that will work with your data. Once you have the field as a column in the results, you can sort by it like on the picture above.
Still I would recommend trying to map createdDate as a date datatype, it would enable a lot of other options (like statistics through visualize).