Modifying meta before saving

Piklist v 0.9.9.8

I have a group filed with 3 fields inside.
How to add another filed to a group before it is saved in meta field?

Now I’m hooking to save_post_$post_type where I retrieve meta filed saved by Piklist, add additional field to group, and update meta filed.

Is there a Piklist hook to do this in one step?

https://ww.wp.xz.cn/plugins/piklist/