When does the magnifying tool disappear? I can't reproduce that on my side, the magnifying glass is always there.

Regarding the circles, it looks strange when the circles are cut out, that was the first version. How about hiding the circles while resizing (when you click on one circle)?

magnifying glass is disappearing for me after I un-press mouse button (after holding CTRL) and widget to resize are is shown (with red border and circles), so it didn't help me when resizing area to exact pixel.
P. S. How can I make a screenshot of screenshot making interface? :)

About circles - maybe replace them to lines outside of area (half of crosshairs), something like typography crop marks?

Now I get you. The Magnifying glass is not missing, it just was not added in the resizer. We can handle this as a new feature request.

What would be the handle with those cropmarks? Also, it kind of is a standard to have a circle or rect as handle, people are used to it. For now I will just make them hidden when you grab one. For more advanced stuff please log a separate issue.

The problem with circles is that they hide the part of corners in snipping area, but they are important for exact fit the area to needed rectangle, for example - to snip rounded corners with radius 3-5 pixel.
If we keep the circles, will be good to see something like this:

There you go, implemented exactly that behavior.