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Suggestion: Output the combined length of all splines

Suggestion: Store each spline's length in an attribute on the spline domain

Alphabetical sorting here too

Alphabetical sorting here too

And here too

Unused includes

I don't think this is used

CurveEval variables are usually just named curve elsewhere.

You can use a reference instead of a pointer here since you already returned early if the geometry set didn't have a curve.
Even though the compiled code will be the same, this helps to show that we don't expect the pointer to be null.

const CurveEval &curve = *curve_set.get_curve_for_read();

profile_spline is probably a variable name you copied from elsewhere? Just spline is better here

You don't need the .get() in this case

Don't forget to set the geometry output in this case, like other early returns in node exec functions.

This can be Span<float> span = attribute.as_span<float>();

You can use a C++ style loop: for (const int i : span.index_range()) {

Been out of the game too long. This is new C++ syntax for me!

Crashes on setting to radius, tilt, position,

no effect on resolution, cyclic (no crash)

Can create new attribute, and update a custom attribute