These files are usually stored in AppData\Roaming\Opera Software\Opera GX Stable .
Using tools like Cookie-Editor to export cookies into the Netscape/TXT format required by other applications. quickcookie-OperaGX.txt
The .txt suffix usually follows the Netscape cookie format , which uses tab-separated values. Which perspective are you interested in exploring further? Cookie-Editor extension - Opera add-ons quickcookie-OperaGX.txt