Often when creating a sketch entities will be used that are for construction purposes only. These entities will not be used to extrude, revolve, etc a solid body but they are important in controlling the sketch entities that will. As complicated geometry is sketched Fusion assumes all sketch entities are candidates for creation of a solid body so it constantly closes/shades closed paths. Once the sketch is completed trimming is usually required to de-clutter the sketch sufficiently to allow the closed profiles that are needed for solid body creation to be easily selected.
One solution to this problem is having the ability to designate construction items within a sketch. So when working in a sketch the user toggles a "for construction" control on or off. Construction lines are colored differently that non-construction lines. Fusion would not attempt to identify closed pathes created by construction lines and would ignore them for solid creation. If a construction entity within the sketch controls a non-sketch entity that does drive solid creation making changes to the construction element could still drive the solid via the influence on non-construction entity.
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