It is totally unclear how to invoke alternative keys - turns out it's a long press gesture. The UI does not show which keys are alternative which I think is poor accessibility.

Perhaps we ought to show the alternative keys? Example: [6, >, ^]. We don't need to show accented characters, since they can be inferred from the context.

Also, some symbols on the keyboard appear truncated: %, ‰, ™ etc., even when they are large.

Reference:
https://github.com/openjdk/jfx/pull/2053#issuecomment-3807091779