isnt it this?
model.set_param_index() or model.set_param_name()
Viewing post in GameMaker Live2D Extension comments
The old version of the SDK was using Live2D's core DLL, so I exported all the low-level interfaces such as manually setting parameters.
The new version of the SDK was modified based on the official Native Framework, and I only connected some of the wrapped functions provided in the Native Framework — the APIs for setting parameters were not exported before.