What?
Extensions (behaviors) can have scene properties, and we, extension users, can edit them in the scene properties panel if any (right click on the scene).
I want extensions (specifically lifecycle functions) can have properties in game properties (next to Firebase, AdMob, Steamworks…).
Why?
Some extensions, for example Newgrounds API and Gamejolt API, require unique static strings to work (API key).
The best function type for initialization is onFirstSceneLoaded, however, since there is no way to enter properties in this lifecycle function without editing the extension, they use a regular action.