where has the curve option gone?

[tyFlow]

Legacy parameters made redundant by Value operators (namely a few curves in some operators, as well as 'relative to property' settings previously available in a few places) have been hidden from the UI, and are only made visible if enabled, so that files remain backwards compatible. This is why you see it in your old file where it was previously enabled, but not in new files. If you're really set on using that setting in new files, you can enable the curve in the operator using MAXScript, as the hidden params are still visible as MAXScript-accessible properties.