6. The aircraft design screen has a list of designs at the bottom. If you tap on them, you just select whatever you tapped on. It would be nice if it also loaded that design in the designer. This will save you a visit to the My Machines tab when you make a new plane or a new variant
7. The Type Designer button in the My Machines tab does not always work correctly. It is supposed to load the design in the designer and switch to it, but it does not always do it; it's a bit buggy. When it fails to work, it still loads the design but does not switch tabs and does not update the name (the name remains whatever it was earlier
8. When you load a design, the family name field (in the designer) loads a design ID, not the actual name you gave that family. The family works correctly anyway, so it's a very minor bug
9. When you design a new version of the plane, the biggest change you can make is switching to a new engine, which has the largest impact. But the New Version function in the My Machines tab blocks the change of family and engine. Family is pretty clear, it is a basis for a plane, but I'm not sure about the engine. You could implement a check that allows you to switch to a different engine of the same size (diameter). This way, switching to an entirely different engine would require redesigning the plane from scratch, but swapping for an updated version of the same engine would be much simpler and take less time to complete