Hi Gaston - MoI does not currently automatically produce mitered corners on stuff like this, so the way to build it now is to use Sweep to generate the surfaces, then use Trim to cut away some excess pieces to make the corners, and a couple of instances of Construct/Planar to build surfaces from a planar set of curves.

That's what I did to create the finished result which is attached here as trim_finished_3dm.zip, which looks like this:



One of the first stages is to select your profile curve, and then do Construct / Sweep to generate the base surfaces. This stage looks like this:



The primary surfaces are created there - use Edit/Separate to separate that into individual surfaces, then select pairs of areas that look like this:



After selecting those overlapping pieces, run Edit/Trim, then at the "Select cutting objects prompt", you push "Done" or right-click without selecting anything else since you want to do a "mutual trim" where each object is acting as both an object to be cut as well as a cutter.

That will calculate the intersections between the surfaces and dice them up into fragments and you can pick which pieces to discard.

Pick these pieces to discard:



To get this final result:



I repeated that for each of those corner areas, for one quarter of the model and then did 2 mirrors to generate the final result.

Let me know if you have questions on any of the stages.

- Michael