Hi! I´m using trim with regions and I don´t know why the output comes out grafted. I want to mantain the data structure the same as the inputs, which its 8 items per branch. Also i don´t know why in somes branches (of the outputs) duplicates the result, giving me a linear curve, and a line-like curve.

What can I use to match the data structure? Making of the output list two items per branch, or the same as the ancestor

You’re trimming 8 curves with one region so the output is grafted to produce a separate branch for each operation. You can restore the input data structure by using the Trim Tree component.

You aren’t providing a Plane input, so it’s using the best fit plane from your input curves. Since your input curves are all straight lines this can produce ambiguous results. Your geometry is all on the World XY plane, so you should provide this at the Plane input.

Seems like you answered your own question there.
Depending of the configuration, Trim with Region may return more than one curve as a result. Since the component may output a list, it needs to graft the input data in all cases for consistency.
If you are sure you get only one curve as a result, then as Kevin said Trim Tree returns your structure.