Thanks for looking into this.
I was able to get that far, the aim is to use Sketch-inner to preserve the middle part and to end up with an engraved path which is roughly the same width throughout. This is derived from a hand-drawn line artwork. The somewhat complex irregular form of the path is intentionally retained to keep the character of the original work.
It is when I try to preserve that little island of material that I get a pocket which has a loop, the path has two forks in it as it goes around this form. That is what seems to create problems for FreeCAD.
I may need to split this up in Inkskape but I need to understand the limitations and requirements of FreeCAD to know what is required, and to be sure this is not just me not knowing how to achieve the result in FreeCAD.
I tried two strategies:
1. making 1mm pad on "sketch inner" to get the body path to preserver it.
2. combining the two lines in Sketchcombo.
I was not able to get the path tools to work on either method. Either by creating a pocket or by directly engraving the outline.
For example, I can get pad and pocket to work on Sketchcombo but I don't see the depth in the 3D view. No errors but I don't see it created. I can not get any of the path tools to work on such a pocket.
That looks like an undetected error in the pocket tool to me but could just as easily be me being dumb
It is quite slow to do the pocket/pad operations due to the complexity of the sketch. Just changing the depth seems to take about 10s to finish.