Hi Danny - this new command is related to Shell or Offset, meaning that it derives a shape directly from existing surfaces and not by introducing any completely new drawn profile curves into the mix.

In the future I definitely do want to be able to do what you are showing there, but I don't think it will be part of this particular command.

Instead my current line of thought is that it would be added as an option to the Booleans.

You can already use a rectangle like that as a cutting object in the Booleans right now, but it produces a hole that goes all the way through the base object. What I'm thinking is that there could be a "Limit depth" checkbox added to the "Select objects to subtract" stage of Boolean difference, and if you checked it and had selected any closed curves as the cutting objects, then that's when you could have an additional stage to the Boolean where you could set a depth and the result would be like you are showing.

Boolean union could be used in a similar way with closed curves to make raised areas instead of indentations.

- Michael