I might have misunderstood your question a bit, so let me show the actual implementation we use — maybe this makes the mechanics clearer.
This works, but it’s clearly a hack:

It requires per‑frame updates.

It fights against the engine’s own auto‑scaling logic (based on player speed).

It’s not performance‑friendly.

https://pastebin.com/93rUSxDv

Yes, ctrlMapAnimAdd does work — the zoom animation itself applies correctly while the key is pressed.

The problem is that as soon as the key is released, the engine immediately restores the minimap to its internal default scale. This happens because the GPS minimap (RscCustomInfoMiniMap) is constantly re-centered and auto-scaled by the engine depending on player speed.

The only way to “fight” this right now is to re-apply ctrlMapAnimAdd every frame to override the engine’s scale, which works but is just a hack and not performance‑friendly.

What this feature request is really about:

Instead of disabling auto-scaling completely, it would be extremely useful to have a config property or script command that lets mission makers/modders define the default minimap scale.

That way, the engine’s auto-scaling would still work (zooming in/out based on speed), but it would operate around a custom baseline zoom level chosen by the player or mod.

This would allow proper manual zoom controls (e.g. PgUp/PgDn) without constantly fighting the engine every frame.