Feature Proposal: Multi-layered input system (modifier-based control layers)

**Description**

Currently, the input system supports complete button mapping, but it feels limited when trying to create more flexible control schemes.

For example, it’s not currently possible to achieve behavior like:

Right stick = Free camera
Holding a button (e.g. LT or RB or whatever the user wants) + Right stick = C buttons

This kind of “hold to switch control context” is common in modern games and would improve usability significantly.

I've read about people apart from myself wanting this functionality in various reddit posts yet it is still not implemented:
https://www.reddit.com/r/SteamDeck/comments/1jbm12w/button_mapping_question_for_ship_of_harkinian/
https://www.reddit.com/r/RG35XXSP/comments/1ndqo7h/ship_of_harkinian_buttons_mapping/

**Proposed Solution**

Introduce a multi-layer input system, where:

- A modifier button activates an alternate input layer
- Each layer can have its own bindings
- Inputs can be mapped as: Default (no modifier), Modifier + input (alternate behavior)

This would allow more flexible and intuitive control setups without having to rely on external tools.

**I'm totally willing to develop this functionality by myself**, but i wanted to ask:

1. Are you interested on this feature?
2. Is someone else already working on this?
3. Is there’s a hidden reason it’s not implemented yet?
4. Do you want me to implement it in a specific way?