@Hyppyayo
There are several ways that S3D could achieve the objective you require but it is likely that none of them will be the same as you have become used to in other software.
This has somewhat similar detail to your requirement:
https://discourse.shapr3d.com/t/aaarrr-creating-a-spoon/5703
You may be able to adapt some of the processes mentioned to achieve the shape needed for the top of the heel.
Then it could be a task for Tools > Subtract to remove the shape from the lofted hell, or Tools > Union to join the shape to the lofted heel.
Please be aware that this is only to give pointers to possible processes.
In this File an Ellipse has been used to form an Oval Body, creating an appropriate Spline Curve would give the exact shape you need. The Spline Curve replacing the Half Ellipse
The Body is then sliced appropriately with a Rectangular Body to enable the removal of the unwanted portion. The remaining portion is hollowed out by Tools > Shell.
Then another Rectangular Body is used to remove the unwanted end of the Oval shape.
Expect a learning curve, someone may jump in with a better alternative.
HollowedShape4MyHeel.shapr (172 KB)