Set Default Name
Enabling this option will have replay generate a name for your capture when you finish recording.
Name Format
The name will start with the date in format YYYYMMDD
(Year, Month, Day), followed by the time the recording was made in the format HHmm-ss
(Hour, minute, seconds).
For example, if I were to record a capture on the date 15/09/2021, at 6:28:00 pm, the capture name generated would be "20210915-1827-00".
Default Name Prefix
The 'Default Name Prefix' field also becomes editable upon enabling the Set Default Name option.

Adding a prefix will insert whatever string you enter at the beginning of the generated name. All together the format will look like:
PrefixYYYYMMDD-HHmm-ss.
It is also possible to manually edit the generated name before saving the recording.