[Solved] Separating tightly fit objects

[pjstock]

dumb simple question (like most of mine) but I have two objects tightly overlayed (a circle inside the borders of a square)
I then Subtracted the circle to make a cutout
I would now like to resize the circle. (or the squiggle which it seems to have turned into when I started messing with the grab points)
But I cannot figure out how to isolate the circle independently to resize it.
Or to delete just the circle object (so I can redraw it)

[keme]

To select an object which is covered by another object, press the Alt key when clicking. First click will select the topmost object, and subsequent clicks will select the next one "down the stack".

You can also use the navigator, but it does not behave very logical when selecting in Draw. You have to drag an object back an forth a little in the navigator before it is selected in the drawing.

[acknak]

You can also press the tab key: this selects each object in turn.

[pjstock]

In my little experiment slide ALT + Click does not appear to do anything at all.

and Tab just toggles between the upper and lower squares (and the drawing within but does not allow me to select just one of the circles.

Now, I am doing this overlay experiment in order to subtract the circle from the square (to get a see through cutout).
Once I do the Modify > Shapes > Subtract to do that, do I now just have one object, the two originals merged into one?
is that why I cannot isolate them?
If so, can I not adjust the shape of the cutout (circle) once I have "Subtracted" it?

(but even then, before I Subtract the ALt+Click seems to do nothing)

[acknak]

... Once I do the Modify > Shapes > Subtract to do that, do I now just have one object, the two originals merged into one?
...

Correct. The Modify operation consumes the selected shapes and leaves only one. The result may have more than one part but they're parts of a single object.

The starting objects are all lost, so it's not possible to adjust the shapes after the Modify operation—at least not in the way they might be adjusted before the Modify.

Because of this, it's often helpful to start out by copying the selected objects to the clipboard, so you can paste in the original objects if needed.

Edit: PS:

The Modify operation also converts everything to a Bezier ("Curve") object, so if you start with a circle object, in the result you no longer have a circle, with that object's behavior, you have a circular shaped curve.

[pjstock]

Got it.
Excellent.
what a great tool Draw is (and resource this forum is)
many thanks (again)