Timelines - change keys at run time (Blueprint) - CurveId?

Greetings, I’m trying to edit the values of a Timeline at runtime. In short, the player can adjust the camera boom length to where they want it in a third person view. I have this length saved to a variable. I am also using a timeline to transition between this length and the length for the ironsite or zoomed in length.

I have found Set Curve Keys which looks like it will do what I need. Problem is, I cant get eny information on CurveId. I assume it is the index of the curve on the name or…

The data type is Animation Curve Identifier Structure I can not find any information on this. I can’t break the struct or edit it if I use it as variable in the editor.

TLDR: How do I get the CurveId?

Thank you for your time.