Structs containing references to instances in the content browser of FloatCurves fail to store these data formats as default values.
This was reported and tested in 4.24.2 (CL-11100242). This was reproduced in 4.23.1 (CL-9631420) and Main 4.26 (CL-11460233)
Results: The FloatCurve reference is lost
Expected: All references are saved when the struct is saved
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-89034 in the post.