It looks like Postman uses LevelDB. On Windows, I found my Postman DB located at:
%HOMEPATH%\AppData\Roaming\Postman\IndexedDB\
ps: %HOMEPATH%
is path for C:\Users\xxxx\
also worth mentioning: %APPDATA%
is a shortcut for C:\Users\xxxx\AppData\Roaming\
According to Piere F, macOS users can find it under:
~/Library/Application Support/Postman/IndexedDB
ps: Note ~
is path for /Users/userAccount/
According to David, Ubuntu users can find it under:
~/.config/Postman/IndexedDB