Populating Custom Tables is currently done either manually or via the REST API. Adding Import from CSV would be a much more user friendly option for the masses to import large volumes of data and would eliminate the need to involve technical resources to leverage the REST API to perform a bulk import/update of a large number of records.
Great to see it's planned.
I have over 70 records that need to be loaded into a custom table and having this CSV import option would really help.