As title, is it possible in Google Data Studio to Convert Unix Timestamp to a human-readable date? For example, to convert '1618087345 to a date format consisting of year month day.
Actually, to treat a field with an Unix timestamp as a date, you don't need to do anything. Just mark the field as "Date & Time" type and you're done.
Check this Data Source and Dashboard as an example:
If you really need to convert manually for whataver reason, you may want to have a look into DATE_FROM_UNIX_DATE function.