Basically, I'm looking to have this specific data structure when it comes to ownership of the games:

Games Collection
│
├── Game 1
│ ├── Service: Steam
│ │ ├── Platform: Windows
│ │ ├── Platform: MacOS
│ │
│ ├── Service: Humble Bundle
│ ├── Platform: Android
│
├── Game 2
│ ├── Service: GOG
│ │ ├── Platform: Windows
│ │ ├── Platform: MacOS
│ │ ├── Platform: Linux
│
├── Game 3
├── Service: Amazon Prime Gaming
│ ├── Platform: Windows
│
├── Service: Humble Bundle
├── Platform: Windows
├── Platform: MacOS

Currently, within KTOMG, the ownership section lets you select the platforms you own the game on. However, let's say that you happen to own this game on two different services (hence my example with Steam and Humble Bundle), with each service providing the game for different platforms, this data structure would allow me to know exactly where I can download the different versions of the games.

Based on my research, no game collection app or website has this capability. I am aware it's a bit niche of a use case.

The Memento DB app allowed me to implement something close to it, with the only issue that I can't filter the games based on the platforms.