Thank you for sending the additional information + files
As you have found by experimenting – Resizing and Offsetting does not give the required results.
It is possible to,
Place Guidelines at the required positions
Node Edit
Drag to select all of the required nodes – include the angled region
Place cursor over a node > Click > Drag > Snap to the required Guideline location
But this is all very manual and I don’t think it’s the appropriate method.
You probably need to be looking for Parametric CAD software that allows the designs to be modified programmatically.
Sorry we couldn’t be more helpful and good luck with the project
Regards,
Tony