Run at project start by user choice (run, don´t run, never run)

No problem - let me know if you do choose to pursue extensible storage for your idea. Specifically, I use it to dump a json array into a string field within a datastorage element as suggested by thumDer

Just to be totally clear, this is shines for storing data that you want centrally accessible to all users within a given project, not a user specific setting.

I had to fumble around interpreting articles with C# examples for a while before I got a grasp of it, i’d be happy to share some python code snippets if it makes your life easier.