OBS allows you to change the pattern for the recordings filenames but there is no simple way to update the file name with any custom string before every recording.
You need to visit the options pane and change settings manualy. The default for the filename formating is: "%CCYY-%MM-%DD %hh-%mm-%ss"
Let's say you've changed the pattern to "MY-HOME-VIDEO %CCYY-%MM-%DD %hh-%mm-%ss" and recorded a file.
Then if you need to make another recording about something else with the prefix "MY-OTHER-VIDEO " you need to change the pattern again, manually.
How to update the filename formating without visiting options pane every time?