If you plan to build with WebGL, there is no need to use Mysql Set Config Action. Use "Use WebGL" Action instead.
Drug mysqlconnection.php file into your webserver public folder or somewhere else.
Make On Start trigger with Use WebGL Action.
Specify the Server File URL (path to this file, for example https://example.com/mysqlconnection.php if file is in root folder)
Use all Mysql Actions without defining Connection Variable